Endoglucanase D (CelD) is a glycoside hydrolase family 9 (GH9) enzyme that catalyzes the endohydrolysis of 1,4-beta-D-glucosidic linkages in cellulose, lichenin, and cereal beta-D-glucans (EC 3.2.1.4). The enzyme is a component of the Acetivibrio thermocellus cellulosome, a large extracellular multi-enzyme complex that efficiently degrades crystalline cellulose. CelD contains a C-terminal type I dockerin domain (residues 579-649) that mediates binding to type I cohesin domains on the scaffoldin protein CipA, enabling incorporation into the cellulosome. The enzyme requires Ca2+ as a cofactor. The dockerin domain contains two EF-hand calcium-binding motifs that are essential for the calcium-dependent cohesin-dockerin interaction. CelD is secreted via a signal peptide (residues 1-41) and functions extracellularly as part of the cellulosome complex anchored to the bacterial cell surface.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0000272
polysaccharide catabolic process
|
IEA
GO_REF:0000120 |
MARK AS OVER ANNOTATED |
Summary: This annotation is derived from InterPro domain mappings (IPR002105 Dockerin, IPR016134 Dockerin domain, IPR036439 Dockerin domain superfamily). While CelD does participate in polysaccharide catabolism, this term is overly broad for an enzyme with well-characterized cellulose-specific activity. The more specific term GO:0030245 'cellulose catabolic process' is already annotated and better captures the function. Deep research confirms CelD is specifically an endo-1,4-beta-glucanase (EC 3.2.1.4) that cleaves internal beta-1,4-glycosidic linkages in cellulose (celD-deep-research-falcon.md).
Reason: The term GO:0000272 'polysaccharide catabolic process' is a parent term of GO:0030245 'cellulose catabolic process'. Since CelD is specifically an endoglucanase (EC 3.2.1.4) that acts on cellulose, lichenin, and cereal beta-D-glucans as stated in UniProt, the more specific cellulose catabolic process term is more appropriate. This IEA annotation from InterPro domain mapping is not incorrect but represents an over-annotation when the more specific term is available.
Supporting Evidence:
file:ACET2/celD/celD-deep-research-falcon.md
CelD is an endo-1,4-beta-glucanase (EC 3.2.1.4) that cleaves internal beta-1,4-glycosidic linkages in cellulose and related beta-glucans
|
|
GO:0004553
hydrolase activity, hydrolyzing O-glycosyl compounds
|
IEA
GO_REF:0000120 |
MARK AS OVER ANNOTATED |
Summary: This annotation is derived from ARBA rule ARBA00027782 and InterPro domains IPR001701 (Glyco_hydro_9) and IPR002105 (Dockerin). While technically correct as CelD does hydrolyze O-glycosyl compounds, this is an overly general term. The more specific GO:0008810 'cellulase activity' is already annotated and better represents the molecular function.
Reason: GO:0004553 'hydrolase activity, hydrolyzing O-glycosyl compounds' is a parent term of GO:0008810 'cellulase activity'. CelD is specifically classified as EC 3.2.1.4 (cellulase/endo-1,4-beta-glucanase) in UniProt with the catalytic activity described as 'Endohydrolysis of (1->4)-beta-D-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans'. The more specific cellulase activity term should be preferred.
Supporting Evidence:
file:ACET2/celD/celD-deep-research-falcon.md
GH9 endoglucanases hydrolyze amorphous cellulose, soluble beta-glucans (e.g., CMC), and contribute to attack on crystalline cellulose
|
|
GO:0005975
carbohydrate metabolic process
|
IEA
GO_REF:0000002 |
MARK AS OVER ANNOTATED |
Summary: This annotation is derived from InterPro2GO mapping based on multiple InterPro domains including IPR001701 (Glyco_hydro_9), IPR004197 (Cellulase_Ig-like), IPR008928 (6-hairpin_glycosidase_sf), and IPR012341 (6hp_glycosidase-like_sf). While correct, this is an extremely broad parent term and the more specific GO:0030245 'cellulose catabolic process' better captures the biological process.
Reason: GO:0005975 'carbohydrate metabolic process' is a very high-level term that encompasses essentially all carbohydrate metabolism. CelD functions specifically in cellulose degradation as evidenced by its UniProt keywords (Cellulose degradation, Glycosidase) and EC classification (3.2.1.4). The GO:0030245 'cellulose catabolic process' annotation already present is far more informative and specific.
Supporting Evidence:
file:ACET2/celD/celD-deep-research-falcon.md
CelD (celD; A3DDN1) from C. thermocellum ATCC 27405 is a secreted, cellulosomal GH9 endoglucanase (EC 3.2.1.4)
|
|
GO:0008810
cellulase activity
|
IEA
GO_REF:0000120 |
ACCEPT |
Summary: This annotation is derived from InterPro domain IPR004197 (Cellulase_Ig-like) and EC number mapping (EC:3.2.1.4). This is the core molecular function of CelD. The UniProt entry explicitly states EC=3.2.1.4 and describes the catalytic activity as 'Endohydrolysis of (1->4)-beta-D-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans'. CelD belongs to glycosyl hydrolase family 9 (GH9) as indicated by CAZy database cross-reference.
Reason: GO:0008810 'cellulase activity' is defined as 'Catalysis of the endohydrolysis of (1->4)-beta-D-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans' which precisely matches the EC 3.2.1.4 classification and catalytic activity description in UniProt for CelD. This is the appropriate molecular function term for an endoglucanase and represents a core function of the protein.
Supporting Evidence:
UniProt:A3DDN1
Endohydrolysis of (1->4)-beta-D-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans.; EC=3.2.1.4
file:ACET2/celD/celD-deep-research-falcon.md
CelD is an endo-1,4-beta-glucanase (EC 3.2.1.4) that cleaves internal beta-1,4-glycosidic linkages in cellulose and related beta-glucans
|
|
GO:0016787
hydrolase activity
|
IEA
GO_REF:0000043 |
MARK AS OVER ANNOTATED |
Summary: This annotation is derived from UniProtKB keyword mapping (KW-0378 Hydrolase). While technically correct, this is an extremely broad term. The more specific GO:0008810 'cellulase activity' already annotated provides much more information about the actual molecular function.
Reason: GO:0016787 'hydrolase activity' is an ancestor term of GO:0008810 'cellulase activity'. For a well-characterized enzyme with specific substrate preferences like CelD (EC 3.2.1.4), retaining such a general term provides no additional information beyond what the specific cellulase activity term already conveys.
Supporting Evidence:
file:ACET2/celD/celD-deep-research-falcon.md
Glycoside hydrolase family 9 (GH9); endo-1,4-beta-glucanase, EC 3.2.1.4
|
|
GO:0016798
hydrolase activity, acting on glycosyl bonds
|
IEA
GO_REF:0000043 |
MARK AS OVER ANNOTATED |
Summary: This annotation is derived from UniProtKB keyword mapping (KW-0326 Glycosidase). While correct, this term is intermediate in specificity between the overly broad 'hydrolase activity' and the appropriately specific 'cellulase activity'. The cellulase activity term is already present and more informative.
Reason: GO:0016798 'hydrolase activity, acting on glycosyl bonds' is a parent term of GO:0008810 'cellulase activity'. Since CelD is specifically classified as a cellulase (EC 3.2.1.4), the more specific term already annotated is preferred and this intermediate term represents redundant annotation.
Supporting Evidence:
file:ACET2/celD/celD-deep-research-falcon.md
CelD is an endo-1,4-beta-glucanase (EC 3.2.1.4) that cleaves internal beta-1,4-glycosidic linkages in cellulose and related beta-glucans
|
|
GO:0030245
cellulose catabolic process
|
IEA
GO_REF:0000043 |
ACCEPT |
Summary: This annotation is derived from UniProtKB keyword mapping (KW-0136 Cellulose degradation). This accurately reflects the biological process in which CelD participates. As an endoglucanase (EC 3.2.1.4) that cleaves internal beta-1,4-glucosidic bonds in cellulose, CelD directly contributes to cellulose catabolism within the cellulosome complex.
Reason: GO:0030245 'cellulose catabolic process' is the appropriate biological process term for CelD. The UniProt entry lists 'Cellulose degradation' as a keyword and describes the function as catalyzing endohydrolysis of glucosidic linkages in cellulose. This is a core function term representing the primary biological role of this endoglucanase in the A. thermocellus cellulosome.
Supporting Evidence:
UniProt:A3DDN1
Endohydrolysis of (1->4)-beta-D-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans.; EC=3.2.1.4
file:ACET2/celD/celD-deep-research-falcon.md
CelD (celD; A3DDN1) from C. thermocellum ATCC 27405 is a secreted, cellulosomal GH9 endoglucanase (EC 3.2.1.4) that integrates via dockerin-cohesin into the CipA scaffold
|
|
GO:0043263
cellulosome
|
ISS
UniProt:A3DDN1 |
NEW |
Summary: This cellular component annotation captures the localization of CelD within the cellulosome complex. CelD contains a type I dockerin domain (residues 579-649) that mediates binding to type I cohesin domains on the scaffoldin CipA. The dockerin domain is annotated in UniProt and literature confirms CelD binding to CipA-derived mini-scaffoldins.
Reason: GO:0043263 'cellulosome' is a critical cellular component annotation that is missing from the current GOA annotations. The UniProt entry clearly indicates CelD has a dockerin domain (residues 579-649) that mediates cellulosome incorporation via cohesin-dockerin interactions. The protein is secreted (signal peptide 1-41) and functions as part of the extracellular cellulosome. Deep research confirms CelD binding to CipA-derived constructs.
Supporting Evidence:
UniProt:A3DDN1
InterPro; IPR002105; Dockerin_1_rpt
file:ACET2/celD/celD-deep-research-falcon.md
CelD is secreted and functions extracellularly as a cellulosomal component tethered to CipA
|
|
GO:1990311
type-I cohesin domain binding
|
ISS
UniProt:A3DDN1 |
NEW |
Summary: CelD contains a type I dockerin domain that specifically binds to type I cohesin domains on scaffoldin proteins like CipA. This molecular function annotation would capture the important cohesin-dockerin interaction that enables cellulosome assembly. The dockerin domain is annotated in UniProt with clear evidence from sequence analysis.
Reason: GO:1990311 'type-I cohesin domain binding' precisely describes the molecular function of the dockerin domain present in CelD. The UniProt entry annotates residues 579-649 as a dockerin domain. Type I dockerins bind type I cohesins, which is how CelD is incorporated into the cellulosome via the CipA scaffoldin. This is a significant molecular function that enables the multi-enzyme complex formation essential for efficient cellulose degradation.
Supporting Evidence:
file:ACET2/celD/celD-deep-research-falcon.md
dockerin-bearing enzymes (including CelD) are recruited via cohesin-dockerin binding
file:ACET2/celD/celD-deep-research-falcon.md
interaction studies demonstrate CelD binding to CipA-derived mini-scaffoldins, confirming a cellulosomal dockerin module
|
|
GO:0005509
calcium ion binding
|
ISS
UniProt:A3DDN1 |
NEW |
Summary: CelD requires Ca2+ as a cofactor as stated in UniProt. The dockerin domain contains two EF-hand calcium-binding sites (PROSITE PS00018) that are essential for the calcium-dependent cohesin-dockerin interaction. This molecular function is important for cellulosome assembly.
Reason: GO:0005509 'calcium ion binding' is supported by multiple lines of evidence in the UniProt entry. The cofactor annotation explicitly states Ca2+ is required. Additionally, two EF-hand calcium-binding sites are annotated via PROSITE PS00018. The dockerin domain function is calcium-dependent, and calcium binding is essential for the cohesin-dockerin interaction that enables cellulosome assembly.
Supporting Evidence:
UniProt:A3DDN1
Name=Ca(2+); Xref=ChEBI:CHEBI:29108; Evidence={ECO:0000250}
UniProt:A3DDN1
InterPro; IPR018247; EF_Hand_1_Ca_BS
|
Q: What is the specific substrate preference of CelD for different beta-glucans (cellulose vs lichenin vs barley beta-glucan)?
Q: What is the synergistic contribution of CelD relative to other cellulosomal endoglucanases?
Q: Are there specific cohesin positions on CipA that preferentially bind CelD?
Experiment: Kinetic characterization of purified CelD with various cellulosic substrates
Hypothesis: CelD has distinct kinetic parameters for cellulose, lichenin, and barley beta-glucan
Experiment: Mutagenesis of dockerin domain calcium-binding residues to confirm calcium dependence
Hypothesis: Calcium binding is essential for cohesin-dockerin interaction
Experiment: Cryo-EM studies of mini-cellulosomes containing CelD to understand spatial arrangement
Hypothesis: CelD adopts a specific orientation when bound to CipA cohesins
provider: falcon
model: Edison Scientific Literature
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start_time: '2025-12-26T17:03:14.371771'
end_time: '2025-12-26T17:13:54.299857'
duration_seconds: 639.93
template_file: templates/gene_research_go_focused.md
template_variables:
organism: ACET2
gene_id: celD
gene_symbol: celD
uniprot_accession: A3DDN1
protein_description: 'RecName: Full=Endoglucanase D; Short=EGD; EC=3.2.1.4; AltName:
Full=Cellulase D; AltName: Full=Endo-1,4-beta-glucanase; Flags: Precursor;'
gene_info: Name=celD; OrderedLocusNames=Cthe_0825;
organism_full: Acetivibrio thermocellus (strain ATCC 27405 / DSM 1237 / JCM 9322
/ NBRC 103400 / NCIMB 10682 / NRRL B-4536 / VPI 7372) (Clostridium thermocellum).
protein_family: Belongs to the glycosyl hydrolase 9 (cellulase E) family.
protein_domains: 6-hairpin_glycosidase_sf. (IPR008928); 6hp_glycosidase-like_sf.
(IPR012341); Cellulase_Ig-like. (IPR004197); Dockerin_1_rpt. (IPR002105); Dockerin_dom.
(IPR016134)
provider_config:
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citation_count: 22
BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.
DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'celD' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information
Please provide a comprehensive research report on the gene celD (gene ID: celD, UniProt: A3DDN1) in ACET2.
The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
Question: You are an expert researcher providing comprehensive, well-cited information.
Provide detailed information focusing on:
1. Key concepts and definitions with current understanding
2. Recent developments and latest research (prioritize 2023-2024 sources)
3. Current applications and real-world implementations
4. Expert opinions and analysis from authoritative sources
5. Relevant statistics and data from recent studies
Format as a comprehensive research report with proper citations. Include URLs and publication dates where available.
Always prioritize recent, authoritative sources and provide specific citations for all major claims.
BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.
DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'celD' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information
Please provide a comprehensive research report on the gene celD (gene ID: celD, UniProt: A3DDN1) in ACET2.
The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
Plan
We verified gene/protein identity, gathered primary and review literature specific to Clostridium thermocellum cellulosomal GH9 endoglucanases with direct evidence for CelD, prioritized recent developments (2023–2024) for cellulosome engineering and applications, extracted mechanistic/localization data, and synthesized findings with specific citations and URLs.
Mandatory verification and disambiguation
- Gene/protein identity: The target is celD encoding Endoglucanase D (EGD), a glycoside hydrolase family 9 (GH9) endo-1,4-β-glucanase integrated into the C. thermocellum cellulosome. Quantitative proteomics of the C. thermocellum ATCC 27405 cellulosome explicitly identifies celD as a GH9 endoglucanase, consistent with UniProt A3DDN1 (organism and functional class match) (gold2007globalviewof pages 1-2).
- Organism: C. thermocellum (syn. Acetivibrio thermocellus) ATCC 27405 is the focal strain in the cited proteomics and cellulosome literature, matching the UniProt record (gold2007globalviewof pages 1-2).
- Family/domains: CelD is a GH9 enzyme bearing a dockerin that mediates attachment to cohesins of the primary scaffoldin CipA; interaction studies demonstrate CelD binding to CipA-derived mini-scaffoldins, confirming a cellulosomal dockerin module consistent with UniProt’s domain annotations (kataeva1997interactionbetweenclostridium pages 1-2, gold2007globalviewof pages 1-2).
- Ambiguity check: Although “celD” is used in other microbes, the sources cited here refer specifically to C. thermocellum Endoglucanase D and its cellulosomal context; thus, identity is confirmed for A3DDN1 (gold2007globalviewof pages 1-2, kataeva1997interactionbetweenclostridium pages 1-2).
Key concepts and definitions
- Function and EC: CelD is an endo-1,4-β-glucanase (EC 3.2.1.4) that cleaves internal β-1,4-glycosidic linkages in cellulose and related β-glucans, classified in GH9. In C. thermocellum, GH9 endoglucanases are major components of the cellulosome and contribute to cellulose depolymerization (gold2007globalviewof pages 1-2, leis2017comparativecharacterizationof pages 1-2).
- Cellulosome architecture: The primary scaffoldin CipA contains multiple type-I cohesins and a CBM that targets cellulose; dockerin-bearing enzymes (including CelD) are recruited via cohesin–dockerin binding. The assembled complex can be anchored to the cell surface via type-II interactions with S-layer proteins, positioning catalytic subunits at the cell–substrate interface (gold2007globalviewof pages 1-2).
Catalytic activity and substrate specificity
- Reaction and substrates: GH9 endoglucanases hydrolyze amorphous cellulose, soluble β-glucans (e.g., CMC), and contribute to attack on crystalline cellulose. Comparative analyses of C. thermocellum cellulosomal cellulases assign a defined hydrolysis product pattern to Cel9D (CelD), placing it among GH9 endoglucanases whose product spectra and processivity differ from GH5 enzymes; inclusion of all endoglucanase types in mini-cellulosomes maximized activity (leis2017comparativecharacterizationof pages 1-2).
- Processivity and product profile: Family-9 enzymes in C. thermocellum can be processive and act on crystalline cellulose; CelI (a noncellulosomal GH9) illustrates GH9 processivity and action on crystalline substrates, a relevant mechanistic analog for CelD within the GH9 family (gilad2003celianoncellulosomal pages 1-2, leis2017comparativecharacterizationof pages 1-2).
Domain architecture, secretion, and localization
- Domain organization: CelD possesses a GH9 catalytic module and a C-terminal dockerin, enabling incorporation into CipA. GH9 enzymes often include auxiliary modules such as CBM3c and Ig-like domains that aid chain feeding and binding; the GH9/CBM3c paradigm is exemplified by CelI and supports the expected architecture/function of CelD (gilad2003celianoncellulosomal pages 1-2, gold2007globalviewof pages 1-2).
- Secretion/localization: CelD is secreted and functions extracellularly as a cellulosomal component tethered to CipA. Binding to CipA-derived constructs bearing a cellulose-binding domain substantially increases CelD’s binding to Avicel and boosts hydrolytic activity, consistent with scaffoldin-mediated targeting to insoluble cellulose (kataeva1997interactionbetweenclostridium pages 1-2, gold2007globalviewof pages 1-2).
Cellulosomal role, synergy, and pathway context
- Synergy: GH9 endoglucanases (e.g., CelD) synergize with GH48 exoglucanases (e.g., Cel48S/CelS) to achieve efficient deconstruction of crystalline cellulose. Designer-cellulosome studies showed that CBM-mediated targeting and GH9–GH48 combinations drive higher activity than proximity alone, emphasizing CelD’s role within balanced consortia of complementary cellulases (vazana2010interplaybetweenclostridium pages 1-2, leis2017comparativecharacterizationof pages 1-2).
- Quantitative effects of scaffoldin targeting: CelD alone displays strong binding to Avicel (~96% bound), and assembling CelD with CBD-bearing mini-scaffoldins increases Avicel binding to ~99% and enhances activity by roughly threefold; cohesin-only constructs decreased binding, underscoring the importance of scaffoldin CBM targeting (kataeva1997interactionbetweenclostridium pages 1-2).
Regulation and expression
- Carbon-source dependence: Quantitative proteomics of the C. thermocellum cellulosome reported carbon source/growth condition-dependent expression of many dockerin-bearing cellulases; this includes GH9 endoglucanases such as CelD and supports adaptive deployment of CelD in response to cellulose versus soluble sugars (gold2007globalviewof pages 1-2).
Recent developments and latest research (prioritizing 2023–2024)
- Proteomics and systems views: Recent large-scale analyses and curated resources reinforce the diversity and modularity of C. thermocellum cellulosome proteins, and highlight the organism’s suitability for consolidated bioprocessing. Reviews and datasets compiled in 2024 emphasize designer/hyperthermostable cellulosomes, diversity of cellulosomal components, and comparative surveys across species, pointing to rational module swaps and CBM engineering to enhance enzyme binding and thermostability (bioRxiv preprint, Nov 2024; include as preprint) (hsin2024lignocellulosedegradationin pages 25-28).
- Cellulosome engineering and CBMs: Contemporary work summarized in recent reviews (2025) indicates targeted enzyme integration via cohesin/dockerin fusions improves hydrolysis, and CBM engineering (including biophysical characterization and “supercharging”) can enhance thermostability and binding—approaches directly relevant to optimizing CelD incorporation into designer cellulosomes (lindic2025structuralandfunctional pages 19-19).
Current applications and implementations
- Designer cellulosomes and enzyme cocktails: Comparative catalogs of C. thermocellum cellulosomal enzymes identified optimal blends where inclusion of GH9 endoglucanases with distinct product profiles (including CelD/Cel9D) maximizes activity; nonavalent mini-cellulosomes achieved about half the activity of native complexes, demonstrating practical assembly strategies for applied enzyme systems (leis2017comparativecharacterizationof pages 1-2).
- Consolidated bioprocessing context: C. thermocellum’s cellulosome is widely exploited for biomass-to-fuels bioprocess design; synergy between GH9 endoglucanases and GH48 exoglucanases in targeted complexes provides a blueprint for industrial cellulase cocktails and live-cell CBP hosts (vazana2010interplaybetweenclostridium pages 1-2, gold2007globalviewof pages 1-2, leis2017comparativecharacterizationof pages 1-2).
Selected statistics and data from recent/primary studies
- Avicel binding and activity modulation by scaffoldin targeting: CelD bound ~96% to Avicel; assembly with CBD-bearing mini-scaffoldins raised binding to ~99% and increased activity ~3×, while cohesin-only constructs reduced binding to 75–79% (kataeva1997interactionbetweenclostridium pages 1-2).
- Product profile and complex performance: A nonavalent mini-cellulosome (nine enzymes bound to CipA) achieved ~50% of native cellulosome activity; inclusion of all four distinct endoglucanase modes (including GH9 types such as Cel9D) was required to reach maximal performance (leis2017comparativecharacterizationof pages 1-2).
Expert opinions and analysis
- Mechanistic role: Within the cellulosome, CelD’s GH9 activity likely contributes processive endoglucanase action and specific product distributions that complement GH5 and GH48 partners, consistent with system-level analyses (leis2017comparativecharacterizationof pages 1-2).
- Design implications: Data demonstrate that CBM-mediated targeting is central; thus, CelD performance in industrial settings should prioritize retention of dockerin for cellulosomal integration or inclusion of appropriate CBMs if deployed as a free enzyme, and pairing with GH48 exoglucanases to maximize crystalline cellulose conversion (vazana2010interplaybetweenclostridium pages 1-2, leis2017comparativecharacterizationof pages 1-2).
Embedded summary of key evidence and applications
| Aspect | Evidence / Details | Key sources |
|---|---|---|
| Identity / organism check | Endoglucanase D (celD; locus Cthe_0825) from Acetivibrio thermocellus / Clostridium thermocellum ATCC 27405; annotated as a GH9 cellulosomal enzyme. | Gold & Martin 2007 J Bacteriol (https://doi.org/10.1128/jb.00882-07) (gold2007globalviewof pages 1-2) |
| Enzyme class & EC | Glycoside hydrolase family 9 (GH9); endo-1,4-β-glucanase, EC 3.2.1.4. | Gold & Martin 2007 (gold2007globalviewof pages 1-2), Leis et al. 2017 (https://doi.org/10.1186/s13068-017-0928-4) (leis2017comparativecharacterizationof pages 1-2) |
| Substrate specificity & product profile | Reported to hydrolyze cellulose; Leis et al. (2017) report a defined hydrolysis product pattern for Cel9D. GH9 enzymes can act on amorphous and crystalline cellulose and may show processive behavior (example: CelI). | Leis 2017 (leis2017comparativecharacterizationof pages 1-2), Gilad 2003 J Bacteriol (https://doi.org/10.1128/jb.185.2.391-398.2003) (gilad2003celianoncellulosomal pages 1-2) |
| Domain architecture | Contains a GH9 catalytic domain and a dockerin for cellulosome integration; GH9s often include CBM3c/CBM3b and Ig-like modules (modular variants exist). | Gilad 2003 (gilad2003celianoncellulosomal pages 1-2), Kataeva 1997 interaction study (kataeva1997interactionbetweenclostridium pages 1-2), Gold 2007 (gold2007globalviewof pages 1-2) |
| Secretion & localization | Secreted and incorporated into the CipA-based cellulosome via dockerin–cohesin binding; scaffoldin CBM(s) and cell-surface anchors target the complex to cellulose. | Kataeva 1997 (kataeva1997interactionbetweenclostridium pages 1-2), Gold & Martin 2007 (gold2007globalviewof pages 1-2), Desvaux 2005 (desvaux2005thecellulosomeof pages 4-4) |
| Interaction / synergy | Binding to scaffoldins (CBD-containing constructs) increases Avicel binding and hydrolytic activity (~3×); synergy with GH48 exoglucanases (and other endoglucanase types) is important for crystalline cellulose breakdown. | Kataeva 1997 (kataeva1997interactionbetweenclostridium pages 1-2), Vazana 2010 AEM (vazana2010interplaybetweenclostridium pages 1-2), Leis 2017 (leis2017comparativecharacterizationof pages 1-2) |
| Regulation / expression | celD and other cellulosomal components show carbon-source/growth-rate-dependent expression; cellulosome proteins are enriched when C. thermocellum is grown on cellulose vs. soluble sugars. | Gold & Martin 2007 (gold2007globalviewof pages 1-2) |
| Selected kinetic / biochemical notes | No detailed kcat/Km for CelD found in gathered evidence; experimental observations include strong Avicel binding (~96%) and activity enhancement when complexed to CBD-bearing scaffoldins. Related GH9s exhibit thermostable optima (e.g., CelI pH 5.5, 70°C). | Kataeva 1997 (kataeva1997interactionbetweenclostridium pages 1-2), Gilad 2003 (gilad2003celianoncellulosomal pages 1-2) |
| Applications / engineering & recent developments | Comparative catalogs and designer-cellulosome studies guide enzyme-cocktail design; proteomics and structural work inform modular reprogramming and targeting strategies relevant to CelD repurposing. | Leis 2017 (leis2017comparativecharacterizationof pages 1-2), Vazana 2010 (vazana2010interplaybetweenclostridium pages 1-2), Lindic & Vodovnik review (lindic2025structuralandfunctional pages 19-19) |
Table: Compact table summarizing verified identity, function, domains, localization, interactions, regulation, and applied/engineering context for CelD (UniProt A3DDN1) in C. thermocellum, with evidence citations for each aspect.
Limitations and open needs
- While CelD identity, cellulosomal integration, and functional class are well supported, detailed CelD-specific kinetic constants and high-resolution structural/domain annotations (e.g., specific CBM modules in CelD) were not found in the retrieved excerpts; further targeted biochemical/structural sources would refine these details (gold2007globalviewof pages 1-2, leis2017comparativecharacterizationof pages 1-2).
- 2023–2024 works directly on CelD are limited in the retrieved set; current insights are drawn from system-level and GH9-related studies and recent reviews/resources (hsin2024lignocellulosedegradationin pages 25-28, lindic2025structuralandfunctional pages 19-19).
Source list with URLs and dates
- Gold ND, Martin VJJ. Global view of the Clostridium thermocellum cellulosome revealed by quantitative proteomic analysis. Journal of Bacteriology. Oct 2007. https://doi.org/10.1128/jb.00882-07 (gold2007globalviewof pages 1-2)
- Leis B, et al. Comparative characterization of all cellulosomal cellulases from Clostridium thermocellum... Biotechnology for Biofuels. Oct 2017. https://doi.org/10.1186/s13068-017-0928-4 (leis2017comparativecharacterizationof pages 1-2)
- Gilad R, et al. CelI, a noncellulosomal family 9 enzyme... Journal of Bacteriology. Jan 2003. https://doi.org/10.1128/jb.185.2.391-398.2003 (gilad2003celianoncellulosomal pages 1-2)
- Vazana Y, et al. Interplay between C. thermocellum family 48 and family 9 cellulases... Applied and Environmental Microbiology. May 2010. https://doi.org/10.1128/aem.00009-10 (vazana2010interplaybetweenclostridium pages 1-2)
- Desvaux M. The cellulosome of Clostridium cellulolyticum. Enzyme and Microbial Technology. Sep 2005. https://doi.org/10.1016/j.enzmictec.2004.04.025 (contextual for cellulosomes) (desvaux2005thecellulosomeof pages 4-4)
- Kataeva I, Guglielmi G, Béguin P. Interaction between C. thermocellum endoglucanase CelD and CipA-derived polypeptides (mini-scaffoldins). 1997; stoichiometry and activity/binding effects (journal URL not provided in excerpt) (kataeva1997interactionbetweenclostridium pages 1-2)
- Hsin K-T, et al. Lignocellulose degradation in bacteria and fungi for biomass conversion. bioRxiv. Nov 2024. https://doi.org/10.1101/2024.11.06.622210 (preprint; systems and design perspectives) (hsin2024lignocellulosedegradationin pages 25-28)
- Lindič N, Vodovnik M. Structural and functional insights into cellulosomes: masters of plant cell wall degradation. Frontiers in Microbiology. Sep 2025. https://doi.org/10.3389/fmicb.2025.1638551 (recent review for engineering context) (lindic2025structuralandfunctional pages 19-19)
Conclusion
CelD (celD; A3DDN1) from C. thermocellum ATCC 27405 is a secreted, cellulosomal GH9 endoglucanase (EC 3.2.1.4) that integrates via dockerin–cohesin into the CipA scaffold. It contributes specific endoglucanase activity and product profiles essential for the high efficiency of the native complex, particularly in synergy with GH48 exoglucanases. Scaffoldin-mediated targeting strongly enhances CelD’s binding and activity on crystalline cellulose. Recent systems and engineering work suggest practical routes—CBM engineering, designer cellulosomes, and targeted enzyme integration—to further leverage CelD in enzyme cocktails and consolidated bioprocessing applications (gold2007globalviewof pages 1-2, leis2017comparativecharacterizationof pages 1-2, kataeva1997interactionbetweenclostridium pages 1-2, vazana2010interplaybetweenclostridium pages 1-2, hsin2024lignocellulosedegradationin pages 25-28).
References
(gold2007globalviewof pages 1-2): Nicholas D. Gold and Vincent J. J. Martin. Global view of the clostridium thermocellum cellulosome revealed by quantitative proteomic analysis. Journal of Bacteriology, 189:6787-6795, Oct 2007. URL: https://doi.org/10.1128/jb.00882-07, doi:10.1128/jb.00882-07. This article has 271 citations and is from a peer-reviewed journal.
(kataeva1997interactionbetweenclostridium pages 1-2): I KATAEVA, G GUGLIELMI, and P BÉGUIN. Interaction between clostridium thermocellum endoglucanase celd and polypeptides derived from the cellulosome-integrating protein cipa: stoichiometry and …. Unknown journal, 1997.
(leis2017comparativecharacterizationof pages 1-2): Benedikt Leis, Claudia Held, Fabian Bergkemper, Katharina Dennemarck, Robert Steinbauer, Alarich Reiter, Matthias Mechelke, Matthias Moerch, Sigrid Graubner, Wolfgang Liebl, Wolfgang H. Schwarz, and Vladimir V. Zverlov. Comparative characterization of all cellulosomal cellulases from clostridium thermocellum reveals high diversity in endoglucanase product formation essential for complex activity. Biotechnology for Biofuels, Oct 2017. URL: https://doi.org/10.1186/s13068-017-0928-4, doi:10.1186/s13068-017-0928-4. This article has 63 citations.
(gilad2003celianoncellulosomal pages 1-2): Rachel Gilad, Larisa Rabinovich, Sima Yaron, Edward A. Bayer, Raphael Lamed, Harry J. Gilbert, and Yuval Shoham. Celi, a noncellulosomal family 9 enzyme from clostridium thermocellum, is a processive endoglucanase that degrades crystalline cellulose. Journal of Bacteriology, 185:391-398, Jan 2003. URL: https://doi.org/10.1128/jb.185.2.391-398.2003, doi:10.1128/jb.185.2.391-398.2003. This article has 165 citations and is from a peer-reviewed journal.
(vazana2010interplaybetweenclostridium pages 1-2): Yael Vazana, Sarah Moraïs, Yoav Barak, Raphael Lamed, and Edward A. Bayer. Interplay between clostridium thermocellum family 48 and family 9 cellulases in cellulosomal versus noncellulosomal states. Applied and Environmental Microbiology, 76:3236-3243, May 2010. URL: https://doi.org/10.1128/aem.00009-10, doi:10.1128/aem.00009-10. This article has 89 citations and is from a peer-reviewed journal.
(hsin2024lignocellulosedegradationin pages 25-28): Kuan-Ting Hsin, HueyTyng Lee, Ying-Chung Jimmy Lin, and Pao-Yang Chen. Lignocellulose degradation in bacteria and fungi for biomass conversion. bioRxiv, Nov 2024. URL: https://doi.org/10.1101/2024.11.06.622210, doi:10.1101/2024.11.06.622210. This article has 2 citations and is from a poor quality or predatory journal.
(lindic2025structuralandfunctional pages 19-19): Nataša Lindič and Maša Vodovnik. Structural and functional insights into cellulosomes: masters of plant cell wall degradation. Frontiers in Microbiology, Sep 2025. URL: https://doi.org/10.3389/fmicb.2025.1638551, doi:10.3389/fmicb.2025.1638551. This article has 1 citations and is from a poor quality or predatory journal.
(desvaux2005thecellulosomeof pages 4-4): Mickaël Desvaux. The cellulosome of clostridium cellulolyticum. Enzyme and Microbial Technology, 37:373-385, Sep 2005. URL: https://doi.org/10.1016/j.enzmictec.2004.04.025, doi:10.1016/j.enzmictec.2004.04.025. This article has 90 citations and is from a peer-reviewed journal.
id: A3DDN1
gene_symbol: celD
product_type: PROTEIN
status: DRAFT
taxon:
id: NCBITaxon:203119
label: Acetivibrio thermocellus (strain ATCC 27405 / DSM 1237 / JCM 9322 / NBRC
103400 / NCIMB 10682 / NRRL B-4536 / VPI 7372)
description: Endoglucanase D (CelD) is a glycoside hydrolase family 9 (GH9) enzyme
that catalyzes the endohydrolysis of 1,4-beta-D-glucosidic linkages in cellulose,
lichenin, and cereal beta-D-glucans (EC 3.2.1.4). The enzyme is a component of the
Acetivibrio thermocellus cellulosome, a large extracellular multi-enzyme complex
that efficiently degrades crystalline cellulose. CelD contains a C-terminal type
I dockerin domain (residues 579-649) that mediates binding to type I cohesin domains
on the scaffoldin protein CipA, enabling incorporation into the cellulosome. The
enzyme requires Ca2+ as a cofactor. The dockerin domain contains two EF-hand calcium-binding
motifs that are essential for the calcium-dependent cohesin-dockerin interaction.
CelD is secreted via a signal peptide (residues 1-41) and functions extracellularly
as part of the cellulosome complex anchored to the bacterial cell surface.
existing_annotations:
- term:
id: GO:0000272
label: polysaccharide catabolic process
evidence_type: IEA
original_reference_id: GO_REF:0000120
review:
summary: This annotation is derived from InterPro domain mappings (IPR002105 Dockerin,
IPR016134 Dockerin domain, IPR036439 Dockerin domain superfamily). While CelD
does participate in polysaccharide catabolism, this term is overly broad for
an enzyme with well-characterized cellulose-specific activity. The more specific
term GO:0030245 'cellulose catabolic process' is already annotated and better
captures the function. Deep research confirms CelD is specifically an endo-1,4-beta-glucanase
(EC 3.2.1.4) that cleaves internal beta-1,4-glycosidic linkages in cellulose
(celD-deep-research-falcon.md).
action: MARK_AS_OVER_ANNOTATED
reason: The term GO:0000272 'polysaccharide catabolic process' is a parent term
of GO:0030245 'cellulose catabolic process'. Since CelD is specifically an endoglucanase
(EC 3.2.1.4) that acts on cellulose, lichenin, and cereal beta-D-glucans as
stated in UniProt, the more specific cellulose catabolic process term is more
appropriate. This IEA annotation from InterPro domain mapping is not incorrect
but represents an over-annotation when the more specific term is available.
supported_by:
- reference_id: file:ACET2/celD/celD-deep-research-falcon.md
supporting_text: CelD is an endo-1,4-beta-glucanase (EC 3.2.1.4) that cleaves
internal beta-1,4-glycosidic linkages in cellulose and related beta-glucans
- term:
id: GO:0004553
label: hydrolase activity, hydrolyzing O-glycosyl compounds
evidence_type: IEA
original_reference_id: GO_REF:0000120
review:
summary: This annotation is derived from ARBA rule ARBA00027782 and InterPro domains
IPR001701 (Glyco_hydro_9) and IPR002105 (Dockerin). While technically correct
as CelD does hydrolyze O-glycosyl compounds, this is an overly general term.
The more specific GO:0008810 'cellulase activity' is already annotated and better
represents the molecular function.
action: MARK_AS_OVER_ANNOTATED
reason: GO:0004553 'hydrolase activity, hydrolyzing O-glycosyl compounds' is a
parent term of GO:0008810 'cellulase activity'. CelD is specifically classified
as EC 3.2.1.4 (cellulase/endo-1,4-beta-glucanase) in UniProt with the catalytic
activity described as 'Endohydrolysis of (1->4)-beta-D-glucosidic linkages in
cellulose, lichenin and cereal beta-D-glucans'. The more specific cellulase
activity term should be preferred.
supported_by:
- reference_id: file:ACET2/celD/celD-deep-research-falcon.md
supporting_text: GH9 endoglucanases hydrolyze amorphous cellulose, soluble beta-glucans
(e.g., CMC), and contribute to attack on crystalline cellulose
- term:
id: GO:0005975
label: carbohydrate metabolic process
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: This annotation is derived from InterPro2GO mapping based on multiple
InterPro domains including IPR001701 (Glyco_hydro_9), IPR004197 (Cellulase_Ig-like),
IPR008928 (6-hairpin_glycosidase_sf), and IPR012341 (6hp_glycosidase-like_sf).
While correct, this is an extremely broad parent term and the more specific
GO:0030245 'cellulose catabolic process' better captures the biological process.
action: MARK_AS_OVER_ANNOTATED
reason: GO:0005975 'carbohydrate metabolic process' is a very high-level term
that encompasses essentially all carbohydrate metabolism. CelD functions specifically
in cellulose degradation as evidenced by its UniProt keywords (Cellulose degradation,
Glycosidase) and EC classification (3.2.1.4). The GO:0030245 'cellulose catabolic
process' annotation already present is far more informative and specific.
supported_by:
- reference_id: file:ACET2/celD/celD-deep-research-falcon.md
supporting_text: CelD (celD; A3DDN1) from C. thermocellum ATCC 27405 is a secreted,
cellulosomal GH9 endoglucanase (EC 3.2.1.4)
- term:
id: GO:0008810
label: cellulase activity
evidence_type: IEA
original_reference_id: GO_REF:0000120
review:
summary: This annotation is derived from InterPro domain IPR004197 (Cellulase_Ig-like)
and EC number mapping (EC:3.2.1.4). This is the core molecular function of CelD.
The UniProt entry explicitly states EC=3.2.1.4 and describes the catalytic activity
as 'Endohydrolysis of (1->4)-beta-D-glucosidic linkages in cellulose, lichenin
and cereal beta-D-glucans'. CelD belongs to glycosyl hydrolase family 9 (GH9)
as indicated by CAZy database cross-reference.
action: ACCEPT
reason: GO:0008810 'cellulase activity' is defined as 'Catalysis of the endohydrolysis
of (1->4)-beta-D-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans'
which precisely matches the EC 3.2.1.4 classification and catalytic activity
description in UniProt for CelD. This is the appropriate molecular function
term for an endoglucanase and represents a core function of the protein.
supported_by:
- reference_id: UniProt:A3DDN1
supporting_text: Endohydrolysis of (1->4)-beta-D-glucosidic linkages in cellulose,
lichenin and cereal beta-D-glucans.; EC=3.2.1.4
- reference_id: file:ACET2/celD/celD-deep-research-falcon.md
supporting_text: CelD is an endo-1,4-beta-glucanase (EC 3.2.1.4) that cleaves
internal beta-1,4-glycosidic linkages in cellulose and related beta-glucans
- term:
id: GO:0016787
label: hydrolase activity
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: This annotation is derived from UniProtKB keyword mapping (KW-0378 Hydrolase).
While technically correct, this is an extremely broad term. The more specific
GO:0008810 'cellulase activity' already annotated provides much more information
about the actual molecular function.
action: MARK_AS_OVER_ANNOTATED
reason: GO:0016787 'hydrolase activity' is an ancestor term of GO:0008810 'cellulase
activity'. For a well-characterized enzyme with specific substrate preferences
like CelD (EC 3.2.1.4), retaining such a general term provides no additional
information beyond what the specific cellulase activity term already conveys.
supported_by:
- reference_id: file:ACET2/celD/celD-deep-research-falcon.md
supporting_text: Glycoside hydrolase family 9 (GH9); endo-1,4-beta-glucanase,
EC 3.2.1.4
- term:
id: GO:0016798
label: hydrolase activity, acting on glycosyl bonds
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: This annotation is derived from UniProtKB keyword mapping (KW-0326 Glycosidase).
While correct, this term is intermediate in specificity between the overly broad
'hydrolase activity' and the appropriately specific 'cellulase activity'. The
cellulase activity term is already present and more informative.
action: MARK_AS_OVER_ANNOTATED
reason: GO:0016798 'hydrolase activity, acting on glycosyl bonds' is a parent
term of GO:0008810 'cellulase activity'. Since CelD is specifically classified
as a cellulase (EC 3.2.1.4), the more specific term already annotated is preferred
and this intermediate term represents redundant annotation.
supported_by:
- reference_id: file:ACET2/celD/celD-deep-research-falcon.md
supporting_text: CelD is an endo-1,4-beta-glucanase (EC 3.2.1.4) that cleaves
internal beta-1,4-glycosidic linkages in cellulose and related beta-glucans
- term:
id: GO:0030245
label: cellulose catabolic process
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: This annotation is derived from UniProtKB keyword mapping (KW-0136 Cellulose
degradation). This accurately reflects the biological process in which CelD
participates. As an endoglucanase (EC 3.2.1.4) that cleaves internal beta-1,4-glucosidic
bonds in cellulose, CelD directly contributes to cellulose catabolism within
the cellulosome complex.
action: ACCEPT
reason: GO:0030245 'cellulose catabolic process' is the appropriate biological
process term for CelD. The UniProt entry lists 'Cellulose degradation' as a
keyword and describes the function as catalyzing endohydrolysis of glucosidic
linkages in cellulose. This is a core function term representing the primary
biological role of this endoglucanase in the A. thermocellus cellulosome.
supported_by:
- reference_id: UniProt:A3DDN1
supporting_text: Endohydrolysis of (1->4)-beta-D-glucosidic linkages in cellulose,
lichenin and cereal beta-D-glucans.; EC=3.2.1.4
- reference_id: file:ACET2/celD/celD-deep-research-falcon.md
supporting_text: CelD (celD; A3DDN1) from C. thermocellum ATCC 27405 is a secreted,
cellulosomal GH9 endoglucanase (EC 3.2.1.4) that integrates via dockerin-cohesin
into the CipA scaffold
- term:
id: GO:0043263
label: cellulosome
evidence_type: ISS
original_reference_id: UniProt:A3DDN1
review:
summary: This cellular component annotation captures the localization of CelD
within the cellulosome complex. CelD contains a type I dockerin domain (residues
579-649) that mediates binding to type I cohesin domains on the scaffoldin CipA.
The dockerin domain is annotated in UniProt and literature confirms CelD binding
to CipA-derived mini-scaffoldins.
action: NEW
reason: GO:0043263 'cellulosome' is a critical cellular component annotation that
is missing from the current GOA annotations. The UniProt entry clearly indicates
CelD has a dockerin domain (residues 579-649) that mediates cellulosome incorporation
via cohesin-dockerin interactions. The protein is secreted (signal peptide 1-41)
and functions as part of the extracellular cellulosome. Deep research confirms
CelD binding to CipA-derived constructs.
additional_reference_ids:
- PMID:8458832
supported_by:
- reference_id: UniProt:A3DDN1
supporting_text: InterPro; IPR002105; Dockerin_1_rpt
- reference_id: file:ACET2/celD/celD-deep-research-falcon.md
supporting_text: CelD is secreted and functions extracellularly as a cellulosomal
component tethered to CipA
- term:
id: GO:1990311
label: type-I cohesin domain binding
evidence_type: ISS
original_reference_id: UniProt:A3DDN1
review:
summary: CelD contains a type I dockerin domain that specifically binds to type
I cohesin domains on scaffoldin proteins like CipA. This molecular function
annotation would capture the important cohesin-dockerin interaction that enables
cellulosome assembly. The dockerin domain is annotated in UniProt with clear
evidence from sequence analysis.
action: NEW
reason: GO:1990311 'type-I cohesin domain binding' precisely describes the molecular
function of the dockerin domain present in CelD. The UniProt entry annotates
residues 579-649 as a dockerin domain. Type I dockerins bind type I cohesins,
which is how CelD is incorporated into the cellulosome via the CipA scaffoldin.
This is a significant molecular function that enables the multi-enzyme complex
formation essential for efficient cellulose degradation.
additional_reference_ids:
- PMID:8458832
supported_by:
- reference_id: file:ACET2/celD/celD-deep-research-falcon.md
supporting_text: dockerin-bearing enzymes (including CelD) are recruited via
cohesin-dockerin binding
- reference_id: file:ACET2/celD/celD-deep-research-falcon.md
supporting_text: interaction studies demonstrate CelD binding to CipA-derived
mini-scaffoldins, confirming a cellulosomal dockerin module
- term:
id: GO:0005509
label: calcium ion binding
evidence_type: ISS
original_reference_id: UniProt:A3DDN1
review:
summary: CelD requires Ca2+ as a cofactor as stated in UniProt. The dockerin domain
contains two EF-hand calcium-binding sites (PROSITE PS00018) that are essential
for the calcium-dependent cohesin-dockerin interaction. This molecular function
is important for cellulosome assembly.
action: NEW
reason: GO:0005509 'calcium ion binding' is supported by multiple lines of evidence
in the UniProt entry. The cofactor annotation explicitly states Ca2+ is required.
Additionally, two EF-hand calcium-binding sites are annotated via PROSITE PS00018.
The dockerin domain function is calcium-dependent, and calcium binding is essential
for the cohesin-dockerin interaction that enables cellulosome assembly.
supported_by:
- reference_id: UniProt:A3DDN1
supporting_text: Name=Ca(2+); Xref=ChEBI:CHEBI:29108; Evidence={ECO:0000250}
- reference_id: UniProt:A3DDN1
supporting_text: InterPro; IPR018247; EF_Hand_1_Ca_BS
core_functions:
- molecular_function:
id: GO:0008810
label: cellulase activity
directly_involved_in:
- id: GO:0030245
label: cellulose catabolic process
locations:
- id: GO:0043263
label: cellulosome
description: CelD functions as an endo-1,4-beta-glucanase (EC 3.2.1.4) that catalyzes
the endohydrolysis of beta-1,4-glucosidic bonds in cellulose. It is a component
of the cellulosome complex where it participates in cellulose degradation.
supported_by:
- reference_id: UniProt:A3DDN1
supporting_text: Endohydrolysis of (1->4)-beta-D-glucosidic linkages in cellulose,
lichenin and cereal beta-D-glucans.; EC=3.2.1.4
- molecular_function:
id: GO:1990311
label: type-I cohesin domain binding
locations:
- id: GO:0043263
label: cellulosome
description: CelD contains a type I dockerin domain that binds to type I cohesin
domains on the scaffoldin protein CipA, enabling incorporation into the cellulosome
complex. This interaction is calcium-dependent.
supported_by:
- reference_id: file:ACET2/celD/celD-deep-research-falcon.md
supporting_text: dockerin-bearing enzymes (including CelD) are recruited via cohesin-dockerin
binding
references:
- id: GO_REF:0000002
title: Gene Ontology annotation through association of InterPro records with GO
terms
findings:
- statement: Provides annotation for carbohydrate metabolic process based on GH9
domain
- id: GO_REF:0000043
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
findings:
- statement: Maps Hydrolase keyword to GO:0016787
- statement: Maps Glycosidase keyword to GO:0016798
- statement: Maps Cellulose degradation keyword to GO:0030245
- id: GO_REF:0000120
title: Combined Automated Annotation using Multiple IEA Methods
findings:
- statement: Provides cellulase activity annotation based on EC:3.2.1.4 and InterPro
domains
- statement: Provides polysaccharide catabolic process from dockerin domain annotations
- id: UniProt:A3DDN1
title: UniProt entry for Endoglucanase D from A. thermocellus
findings:
- statement: EC 3.2.1.4 classification confirms cellulase activity
supporting_text: 'RecName: Full=Endoglucanase D; Short=EGD; EC=3.2.1.4'
- statement: Dockerin domain enables cellulosome incorporation
supporting_text: InterPro; IPR002105; Dockerin_1_rpt
- statement: Ca2+ cofactor required with EF-hand binding sites
supporting_text: Name=Ca(2+); Xref=ChEBI:CHEBI:29108; Evidence={ECO:0000250}
- statement: Signal peptide indicates secreted protein
supporting_text: 'AltName: Full=Endo-1,4-beta-glucanase; Flags: Precursor'
- statement: GH9 family member per CAZy database
supporting_text: CAZy; GH9; Glycoside Hydrolase Family 9
- id: PMID:3024110
title: Nucleotide sequence of the cellulase gene celD encoding endoglucanase D
full_text_unavailable: true
- id: PMID:8458832
title: Organization of a Clostridium thermocellum gene cluster encoding the cellulosomal
scaffolding protein CipA
findings:
- statement: Demonstrates CelD binds to cellulosome scaffoldin proteins via dockerin
domain
supporting_text: it was found previously that ORF3p binds 125I-labeled endoglucanase
CelD containing the duplicated segment
- id: file:ACET2/celD/celD-deep-research-falcon.md
title: Deep research summary for CelD
findings:
- statement: CelD is a GH9 endoglucanase that integrates into the cellulosome via
dockerin-cohesin interaction
supporting_text: CelD (celD; A3DDN1) from C. thermocellum ATCC 27405 is a secreted,
cellulosomal GH9 endoglucanase (EC 3.2.1.4) that integrates via dockerin-cohesin
into the CipA scaffold
- statement: Scaffoldin-mediated targeting enhances CelD binding and activity on
crystalline cellulose
supporting_text: Scaffoldin-mediated targeting strongly enhances CelD's binding
and activity on crystalline cellulose
proposed_new_terms: []
suggested_questions:
- question: What is the specific substrate preference of CelD for different beta-glucans
(cellulose vs lichenin vs barley beta-glucan)?
- question: What is the synergistic contribution of CelD relative to other cellulosomal
endoglucanases?
- question: Are there specific cohesin positions on CipA that preferentially bind
CelD?
suggested_experiments:
- description: Kinetic characterization of purified CelD with various cellulosic substrates
hypothesis: CelD has distinct kinetic parameters for cellulose, lichenin, and barley
beta-glucan
- description: Mutagenesis of dockerin domain calcium-binding residues to confirm
calcium dependence
hypothesis: Calcium binding is essential for cohesin-dockerin interaction
- description: Cryo-EM studies of mini-cellulosomes containing CelD to understand
spatial arrangement
hypothesis: CelD adopts a specific orientation when bound to CipA cohesins
tags:
- cellulosome