EngK is a glycoside hydrolase family 9 (GH9) endoglucanase from the Clostridium cellulovorans cellulosome. It contains an N-terminal signal peptide, a GH9 catalytic domain, a CBM4 carbohydrate-binding module, and a C-terminal type I dockerin domain for cellulosome assembly. EngK catalyzes endo-1,4-β-glucanase activity, cleaving internal β-1,4-glycosidic bonds in cellulose to produce primarily cellobiose. It synergizes with the GH48 exoglucanase ExgS for efficient cellulose hydrolysis and shows reduced sensitivity to cellobiose inhibition compared to EngH.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0000272
polysaccharide catabolic process
|
IEA
GO_REF:0000120 |
ACCEPT |
Summary: This annotation is correct. EngK is an endoglucanase that directly participates in polysaccharide (cellulose) catabolism by hydrolyzing β-1,4-glycosidic bonds.
Reason: As a GH9 endoglucanase, EngK directly catalyzes the breakdown of polysaccharides. This is a core function supported by biochemical characterization.
Supporting Evidence:
file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
Biochemical assays of recombinant EngK from C. cellulovorans demonstrate endo-1,4-β-glucanase activity
|
|
GO:0004553
hydrolase activity, hydrolyzing O-glycosyl compounds
|
IEA
GO_REF:0000120 |
KEEP AS NON CORE |
Summary: This annotation is correct but generic. EngK has hydrolase activity on O-glycosyl bonds. More specific terms like GO:0008810 (cellulase activity) better capture its function.
Reason: This is a true parent term of the more specific cellulase activity. It's correct but not the most informative annotation for this enzyme.
Supporting Evidence:
file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
GH9 endoglucanases are modular cellulases that cleave internal β-1,4-glycosidic bonds of cellulose
|
|
GO:0005975
carbohydrate metabolic process
|
IEA
GO_REF:0000002 |
MARK AS OVER ANNOTATED |
Summary: This annotation is too general. EngK participates in cellulose catabolism specifically, not general carbohydrate metabolism. More specific terms exist.
Reason: This parent term is overly broad. GO:0030245 (cellulose catabolic process) is the appropriate specific term for EngK function.
Supporting Evidence:
file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
GH9 endoglucanases are modular cellulases that cleave internal β-1,4-glycosidic bonds of cellulose
|
|
GO:0008810
cellulase activity
|
IEA
GO_REF:0000002 |
ACCEPT |
Summary: This annotation is correct and represents a core molecular function of EngK. As a GH9 endoglucanase, EngK has cellulase activity that hydrolyzes cellulose.
Reason: EngK is a GH9 family cellulase with demonstrated endo-1,4-β-glucanase activity. This is the appropriate molecular function annotation.
Supporting Evidence:
file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
Biochemical assays of recombinant EngK from C. cellulovorans demonstrate endo-1,4-β-glucanase activity that yields predominantly cellobiose
|
|
GO:0016787
hydrolase activity
|
IEA
GO_REF:0000043 |
MARK AS OVER ANNOTATED |
Summary: This annotation is too general. EngK has hydrolase activity, but more specific terms like cellulase activity better describe its function.
Reason: This is a very broad parent term. GO:0008810 (cellulase activity) is the appropriate level of specificity for this GH9 enzyme.
Supporting Evidence:
file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
GH9 family endoglucanase
|
|
GO:0016798
hydrolase activity, acting on glycosyl bonds
|
IEA
GO_REF:0000120 |
KEEP AS NON CORE |
Summary: This annotation is correct but not as specific as GO:0008810. EngK acts on glycosyl bonds in cellulose.
Reason: This is a parent term of cellulase activity. It's correct but less informative than the more specific GO:0008810 annotation.
Supporting Evidence:
file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
cleave internal β-1,4-glycosidic bonds of cellulose
|
|
GO:0030245
cellulose catabolic process
|
IEA
GO_REF:0000043 |
ACCEPT |
Summary: This annotation is correct and represents the core biological process for EngK. As an endoglucanase, EngK directly participates in cellulose degradation.
Reason: EngK is a cellulosomal endoglucanase that catalyzes cellulose hydrolysis. This is the appropriate biological process annotation.
Supporting Evidence:
file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
EngK is a GH9 family endoglucanase from Clostridium cellulovorans; described as a cellulosomal subunit
|
|
GO:0043263
cellulosome
|
TAS
file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md |
NEW |
Summary: EngK is a cellulosomal enzyme that assembles into the cellulosome via its dockerin domain. This cellular component annotation is essential.
Reason: EngK contains a type I dockerin domain and was identified as a cellulosomal subunit by cohesin-affinity profiling.
Supporting Evidence:
file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
EngK detected as dockerin-bearing (thus cellulosomal)
|
|
GO:0005576
extracellular region
|
TAS
file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md |
NEW |
Summary: EngK is secreted and functions extracellularly as part of the cellulosome. It has a signal peptide for secretion.
Reason: EngK contains a signal peptide (residues 1-23) and is secreted to function in the extracellular cellulosome complex.
Supporting Evidence:
file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
EngK is secreted and incorporated into extracellular cellulosome complexes via its dockerin domain
|
|
GO:1990311
type-I cohesin domain binding
|
TAS
file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md |
NEW |
Summary: EngK contains a type I dockerin domain that binds to type I cohesins on the CbpA scaffoldin, enabling cellulosome assembly.
Reason: The dockerin domain mediates binding to cohesin domains, which is essential for cellulosome incorporation.
Supporting Evidence:
file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
C-terminal dockerin (cellulosome-targeting)
|
|
GO:0044575
cellulosome assembly
|
NAS | NEW |
Summary: Added to align core_functions with existing annotations.
Reason: Core function term not present in existing_annotations.
|
Q: What is the structural basis for EngK's reduced sensitivity to cellobiose inhibition compared to EngH?
Experiment: Detailed kinetic characterization of EngK on various cellulose substrates to determine Km, kcat, and product profile.
Hypothesis: EngK may have a distinct active site architecture that favors cellobiose release and reduces product inhibition.
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template_file: templates/gene_research_go_focused.md
template_variables:
organism: CLOCL
gene_id: Q9RGE8
gene_symbol: engK
uniprot_accession: Q9RGE8
protein_description: 'RecName: Full=Glucanase {ECO:0000256|RuleBase:RU361166}; EC=3.2.1.-
{ECO:0000256|RuleBase:RU361166};'
gene_info: Name=engK {ECO:0000313|EMBL:AAF06107.1};
organism_full: Clostridium cellulovorans.
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); CenC_carb-bd. (IPR003305); Dockerin_1_rpt.
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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 'engK' 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 engK (gene ID: Q9RGE8, UniProt: Q9RGE8) in CLOCL.
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 'engK' 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 engK (gene ID: Q9RGE8, UniProt: Q9RGE8) in CLOCL.
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 and verification summary
Objective 1 (identity) was completed. The gene symbol engK in Clostridium cellulovorans encodes a glycoside hydrolase family 9 (GH9) endoglucanase that is a dockerin-bearing cellulosomal subunit, matching UniProt Q9RGE8 and the domain expectations for GH9 cellulosomal enzymes. No conflicting use of engK in other organisms was found in the consulted literature (cho2010cellulosomicprofilingproduced pages 3-5, demain2005cellulaseclostridiaand pages 9-10).
Key concepts and definitions
Glycoside hydrolase family 9 (GH9) endoglucanases are modular cellulases that cleave internal β-1,4-glycosidic bonds of cellulose. In cellulosomal systems, GH9s often work with GH48 exoglucanases to convert cellulose to cellodextrins and cellobiose. Dockerin–cohesin interactions assemble these enzymes onto scaffoldins to form extracellular cellulosomes that can attach to cellulose and, in many species, to the bacterial surface (demain2005cellulaseclostridiaand pages 9-10, schwarz2004extracellularglycosylhydrolases pages 19-22, leis2017comparativecharacterizationof pages 12-13).
Recent developments and latest research (prioritize 2023–2024)
Two recent lines of evidence contextualize EngK. First, a 2024 review synthesizes current understanding of cellulase systems in soils and highlights the prevalence and roles of GH9 enzymes in cellulose depolymerization, reinforcing their centrality in natural lignocellulose conversion (Heliyon, 2024-01; https://doi.org/10.1016/j.heliyon.2024.e24022) (). Second, a 2024 genomic survey reveals continuing discovery of cellulosome-producing bacteria and diversity in their GH complements and regulation, underscoring the modular principles that also apply to C. cellulovorans cellulosomes (Frontiers in Microbiology, 2024-10; https://doi.org/10.3389/fmicb.2024.1473396) (). Within GH9s, mechanistic diversity in product patterns and processivity remains a focus, with comparative cellulosomal studies delineating four product-pattern types that inform cellulosome engineering (Biotechnology for Biofuels, 2017-10; https://doi.org/10.1186/s13068-017-0928-4) (leis2017comparativecharacterizationof pages 12-13).
Function, catalytic activity, and product profile of EngK
Biochemical assays of recombinant EngK from C. cellulovorans demonstrate endo-1,4-β-glucanase activity that yields predominantly cellobiose and short oligos; notably, products larger than cellotriose were not observed under the reported assay conditions. EngK acts on cellotriose and generates ≤DP3 products, consistent with a processive endoglucanase biased toward cellobiose release (AMB Express, 2016-01; https://doi.org/10.1186/s13568-015-0169-5) (yamamoto2016synergisticpropertiesof pages 3-4, yamamoto2016synergisticpropertiesof pages 1-3).
Domain architecture and cellulosomal status
Experimental proteomic profiling using a cohesin marker identified EngK as a dockerin-bearing, cellulosomal enzyme secreted by C. cellulovorans across multiple carbon sources, consistent with the GH9 catalytic core flanked by ancillary domains and a C-terminal dockerin. Classical architecture for GH9 cellulosomal enzymes includes an N-terminal Ig-like domain and a family 3c carbohydrate-binding module (CBM3c) adjacent to the catalytic domain, sometimes accompanied by CBM3b; the CBM3c is often essential for activity and can promote processivity by aligning substrate in the active-site cleft. These features align with the UniProt domain expectations (Ig-like, CBM/CBM-like, dockerin I) for EngK (Journal of Biotechnology, 2010-02; https://doi.org/10.1016/j.jbiotec.2009.11.020; Microbiol Mol Biol Rev, 2005-03; https://doi.org/10.1128/mmbr.69.1.124-154.2005; Adv Appl Microbiol, 2004-01; https://doi.org/10.1016/S0065-2164(04)56007-0) (cho2010cellulosomicprofilingproduced pages 3-5, demain2005cellulaseclostridiaand pages 9-10, schwarz2004extracellularglycosylhydrolases pages 19-22).
Cellular/extracellular localization
EngK is secreted and incorporated into extracellular cellulosome complexes via its dockerin domain, as demonstrated by cohesin-affinity profiling. Cellulosomes assemble on scaffoldins and can be cell-associated, positioning catalytic subunits like EngK in close proximity to cellulose at the cell–substrate interface (Journal of Biotechnology, 2010-02; https://doi.org/10.1016/j.jbiotec.2009.11.020; Microbiol Mol Biol Rev, 2005-03; https://doi.org/10.1128/mmbr.69.1.124-154.2005) (cho2010cellulosomicprofilingproduced pages 3-5, demain2005cellulaseclostridiaand pages 9-10).
Synergy with ExgS (GH48) and inhibition by cellobiose
EngK synergizes with the GH48 exoglucanase ExgS on acid-swollen cellulose. Although the ExgS+EngK pair showed lower maximal specific activity than ExgS+EngH, EngK+ExgS retained more activity in the presence of product inhibitor cellobiose: at 5 mg/mL cellobiose, EngK+ExgS activity was more than twice that of EngH+ExgS, whereas at 10 mg/mL activity was abolished for both. Structural modeling suggests EngK has fewer aromatic residues in the active-site cleft than EngH, potentially explaining its different product profile and reduced sensitivity to cellobiose (AMB Express, 2016-01; https://doi.org/10.1186/s13568-015-0169-5) (yamamoto2016synergisticpropertiesof pages 3-4, yamamoto2016synergisticpropertiesof pages 4-5).
GH9 roles in cellulosome efficiency and processivity
Comparative studies of cellulosomal GH9s reveal diverse hydrolysis modes, including processive endoglucanases that preferentially release cellobiose (pEG2) or cellotetraose (pEG4). A CBM3c adjoining the GH9 catalytic domain is often aligned with the active-site groove and reduces dissociation, increasing processivity. GH9–GH48 synergy on crystalline cellulose is strong and ratio-dependent; enforced proximity (e.g., in fusion constructs) enhances activity, highlighting the cellulosome’s architectural advantage (Biotechnol Biofuels, 2017-10; https://doi.org/10.1186/s13068-017-0928-4; Adv Appl Microbiol, 2004-01; https://doi.org/10.1016/S0065-2164(04)56007-0) (leis2017comparativecharacterizationof pages 12-13, schwarz2004extracellularglycosylhydrolases pages 19-22).
Regulation of cellulosomal composition in C. cellulovorans
Cohesin-affinity proteomics showed that dockerin-bearing subunit repertoires, including EngK, vary with carbon source (Avicel, xylan, AXP, cellobiose). Approximately 16–17 dockerin-containing proteins were detected depending on substrate, and relative abundances of core enzymes (e.g., EngH, ExgS) shifted, indicating environmental tuning of the cellulosome. EngK was identified among major, consistently produced cellulosomal enzymes across conditions, consistent with a role in core cellulose depolymerization (Journal of Biotechnology, 2010-02; https://doi.org/10.1016/j.jbiotec.2009.11.020) (cho2010cellulosomicprofilingproduced pages 3-5).
Current applications and real-world implementations
The mechanistic insights from GH9 diversity and GH9–GH48 synergy guide enzyme cocktail formulation and synthetic cellulosome design for biomass conversion. Reviews and surveys from 2024 emphasize GH9 prevalence in environmental cellulose turnover and the expanding catalog of cellulosome-producing bacteria, informing bioprospecting and engineering strategies for consolidated bioprocessing. The principles of dockerin–cohesin assembly and CBM3c-enhanced processivity are now widely used in constructing designer cellulosomes and fusion enzymes to improve activity on recalcitrant substrates (Heliyon, 2024-01; https://doi.org/10.1016/j.heliyon.2024.e24022; Front Microbiol, 2024-10; https://doi.org/10.3389/fmicb.2024.1473396; Biotechnol Biofuels, 2017-10; https://doi.org/10.1186/s13068-017-0928-4) (leis2017comparativecharacterizationof pages 12-13).
Expert opinions and authoritative analyses
Authoritative reviews synthesize that GH9 enzymes are core to cellulosome function, with CBM3c and Ig-like modules modulating catalysis and stability, and that enzyme diversity within the complex is essential for high cellulolytic efficiency on crystalline cellulose. The classical MMBR review and Advances in Applied Microbiology analysis articulate how cellulosomal proximity effects, substrate anchoring via scaffoldin CBMs, and dockerin–cohesin specificity translate into superior hydrolysis rates relative to free-enzyme systems (Microbiol Mol Biol Rev, 2005-03; https://doi.org/10.1128/mmbr.69.1.124-154.2005; Adv Appl Microbiol, 2004-01; https://doi.org/10.1016/S0065-2164(04)56007-0) (demain2005cellulaseclostridiaand pages 9-10, schwarz2004extracellularglycosylhydrolases pages 19-22).
Relevant statistics and data from recent studies
- EngK+ExgS maximal specific activity on swollen cellulose: 0.119 U/μmol; ExgS+EngH: 0.251 U/μmol. At 5 mg/mL cellobiose, EngK+ExgS retains >2× activity relative to EngH+ExgS; both inhibited completely at 10 mg/mL (AMB Express, 2016-01; https://doi.org/10.1186/s13568-015-0169-5) (yamamoto2016synergisticpropertiesof pages 3-4).
- Substrate-dependent composition: ~16 dockerin-containing proteins on Avicel; ~17 on xylan/AXP; EngK consistently detected among major subunits by cohesin marker profiling (Journal of Biotechnology, 2010-02; https://doi.org/10.1016/j.jbiotec.2009.11.020) (cho2010cellulosomicprofilingproduced pages 3-5).
- GH9 product-pattern classes in cellulosomes: exo/CBH-like, non-processive EG, processive EG producing cellotetraose (pEG4), and processive EG producing cellobiose (pEG2), with CBM3c promoting processivity (Biotechnol Biofuels, 2017-10; https://doi.org/10.1186/s13068-017-0928-4) (leis2017comparativecharacterizationof pages 12-13).
Limitations
Direct domain-mapping for EngK (e.g., exact presence of CBM3c and Ig-like modules) was inferred from family- and species-level patterns and dockerin-based proteomics; EngK’s precise domain composition in Q9RGE8 should be confirmed with full-length sequence/domain annotation resources or targeted structural studies. Nonetheless, the dockerin-bearing, cellulosomal GH9 identity and functional properties are well supported by experimental studies in C. cellulovorans (cho2010cellulosomicprofilingproduced pages 3-5, yamamoto2016synergisticpropertiesof pages 3-4, demain2005cellulaseclostridiaand pages 9-10).
Embedded artifact
| Aspect | Evidence / Details (citations) | Key data / statistics | Source (journal, year, URL) |
|---|---|---:|---|
| Identity / organism | EngK is a GH9 family endoglucanase from Clostridium cellulovorans; described as a cellulosomal subunit matching UniProt Q9RGE8 (engK). (cho2010cellulosomicprofilingproduced pages 3-5, demain2005cellulaseclostridiaand pages 9-10) | Gene/protein: engK (UniProt Q9RGE8); organism: Clostridium cellulovorans | Cho W. et al., Journal of Biotechnology, 2010. https://doi.org/10.1016/j.jbiotec.2009.11.020 (cho2010cellulosomicprofilingproduced pages 3-5) |
| Catalytic function & main products | Biochemical assays on recombinant EngK show endo-1,4-β-glucanase activity; products reported as primarily cellobiose and/or short oligos (no products > cellotriose reported in assays). (yamamoto2016synergisticpropertiesof pages 3-4, yamamoto2016synergisticpropertiesof pages 1-3) | Produces mainly cellobiose; acts on cellotriose and yields ≤ DP3 products in assay conditions | Yamamoto K. & Tamaru Y., AMB Express, 2016. https://doi.org/10.1186/s13568-015-0169-5 (yamamoto2016synergisticpropertiesof pages 3-4, yamamoto2016synergisticpropertiesof pages 1-3) |
| Synergy with ExgS (GH48) & cellobiose inhibition | EngK + ExgS show synergistic hydrolysis on swollen/acid-treated cellulose; combination is inhibited by cellobiose but the EngK+ExgS pair is less sensitive to 5 mg/mL cellobiose than EngH+ExgS. Structural modeling links fewer aromatic subsites in EngK to altered product profile and reduced inhibition. (yamamoto2016synergisticpropertiesof pages 3-4, yamamoto2016synergisticpropertiesof pages 4-5) | Reported specific activity: ExgS+EngK = 0.119 U/μmol vs ExgS+EngH = 0.251 U/μmol; EngK+ExgS retains >2× relative activity vs EngH+ExgS at 5 mg/mL cellobiose (no activity at 10 mg/mL). | Yamamoto K. & Tamaru Y., AMB Express, 2016. https://doi.org/10.1186/s13568-015-0169-5 (yamamoto2016synergisticpropertiesof pages 3-4, yamamoto2016synergisticpropertiesof pages 4-5) |
| Domain architecture & cellulosomal status | GH9 catalytic module commonly associated with CBM3c (or other CBMs), sometimes Ig-like modules and C-terminal dockerin; EngK is detected as dockerin-bearing (thus cellulosomal). Domain annotations consistent with GH9 modular patterns in clostridia. (demain2005cellulaseclostridiaand pages 9-10, schwarz2004extracellularglycosylhydrolases pages 19-22, cho2010cellulosomicprofilingproduced pages 3-5) | Modular organization: GH9 catalytic domain ± CBM3c/CBM3b and Ig-like module; C-terminal dockerin (cellulosome-targeting) reported for EngK | Demain A.L. et al., Microbiol Mol Biol Rev, 2005. https://doi.org/10.1128/mmbr.69.1.124-154.2005 (demain2005cellulaseclostridiaand pages 9-10); Schwarz W.H. et al., Adv Appl Microbiol, 2004. https://doi.org/10.1016/S0065-2164(04)56007-0 (schwarz2004extracellularglycosylhydrolases pages 19-22); Cho W. et al., 2010 (cho2010cellulosomicprofilingproduced pages 3-5) |
| Localization (extracellular / cellulosome association) | EngK detected among cohesin-binding (dockerin-containing) extracellular proteins; cellulosomal enzymes are secreted and assemble extracellularly on scaffoldins (e.g., CbpA/CipA) and can be cell-associated. (cho2010cellulosomicprofilingproduced pages 3-5, demain2005cellulaseclostridiaand pages 9-10) | Detected in extracellular proteome by cohesin marker; part of extracellular cellulosome complexes | Cho W. et al., Journal of Biotechnology, 2010. https://doi.org/10.1016/j.jbiotec.2009.11.020 (cho2010cellulosomicprofilingproduced pages 3-5); Demain A.L. et al., 2005 (demain2005cellulaseclostridiaand pages 9-10) |
| GH9 roles in processivity & product patterns | GH9 family shows four product-pattern classes (exo/CBH-like, non-processive EG, processive EG yielding cellotetraose pEG4, and processive pEG2 yielding cellobiose); CBM3c adjacent to GH9 often promotes processivity by aligning substrate and reducing koff. (leis2017comparativecharacterizationof pages 12-13, schwarz2004extracellularglycosylhydrolases pages 19-22) | GH9 diversity underpins processivity spectrum; CBM3c modulates processivity and product DP (Leis et al. 2017) | Leis B. et al., Biotechnol Biofuels, 2017. https://doi.org/10.1186/s13068-017-0928-4 (leis2017comparativecharacterizationof pages 12-13); Schwarz W.H. et al., 2004 (schwarz2004extracellularglycosylhydrolases pages 19-22) |
| Regulation of cellulosome composition vs carbon source | Proteomic/cohesin-marker profiling shows substrate-dependent variation in dockerin-bearing subunits; EngK is among major, consistently produced cellulosomal enzymes but relative abundances shift with carbon source (Avicel, xylan, cellobiose, etc.). (cho2010cellulosomicprofilingproduced pages 3-5, demain2005cellulaseclostridiaand pages 9-10) | Example: ~16 dockerin-containing proteins on Avicel; composition and relative intensities of EngH/ExgS/EngK vary by substrate. | Cho W. et al., Journal of Biotechnology, 2010. https://doi.org/10.1016/j.jbiotec.2009.11.020 (cho2010cellulosomicprofilingproduced pages 3-5); Demain A.L. et al., 2005 (demain2005cellulaseclostridiaand pages 9-10) |
Table: Compact evidence table summarizing EngK identity, function, modular architecture, localization, synergy/inhibition data, GH9 processivity roles, and substrate-dependent regulation; citations link each claim to the underlying literature contexts (yamamoto2016synergisticpropertiesof pages 3-4, cai2000analysisofcellulolytic pages 21-27).
References
(cho2010cellulosomicprofilingproduced pages 3-5): Woojae Cho, Sang Duck Jeon, Hyun Jung Shim, Roy H. Doi, and Sung Ok Han. Cellulosomic profiling produced by clostridium cellulovorans during growth on different carbon sources explored by the cohesin marker. Journal of biotechnology, 145 3:233-9, Feb 2010. URL: https://doi.org/10.1016/j.jbiotec.2009.11.020, doi:10.1016/j.jbiotec.2009.11.020. This article has 39 citations and is from a peer-reviewed journal.
(demain2005cellulaseclostridiaand pages 9-10): Arnold L. Demain, Michael Newcomb, and J. H. David Wu. Cellulase, clostridia, and ethanol. Microbiology and Molecular Biology Reviews, 69:124-154, Mar 2005. URL: https://doi.org/10.1128/mmbr.69.1.124-154.2005, doi:10.1128/mmbr.69.1.124-154.2005. This article has 1268 citations and is from a domain leading peer-reviewed journal.
(schwarz2004extracellularglycosylhydrolases pages 19-22): Wolfgang H. Schwarz, Vladimir V. Zverlov, and Hubert Bahl. Extracellular glycosyl hydrolases from clostridia. Advances in applied microbiology, 56:215-61, Jan 2004. URL: https://doi.org/10.1016/s0065-2164(04)56007-0, doi:10.1016/s0065-2164(04)56007-0. This article has 65 citations.
(leis2017comparativecharacterizationof pages 12-13): 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.
(yamamoto2016synergisticpropertiesof pages 3-4): Kosuke Yamamoto and Yutaka Tamaru. Synergistic properties of cellulases from clostridium cellulovorans in the presence of cellobiose. AMB Express, Jan 2016. URL: https://doi.org/10.1186/s13568-015-0169-5, doi:10.1186/s13568-015-0169-5. This article has 17 citations and is from a peer-reviewed journal.
(yamamoto2016synergisticpropertiesof pages 1-3): Kosuke Yamamoto and Yutaka Tamaru. Synergistic properties of cellulases from clostridium cellulovorans in the presence of cellobiose. AMB Express, Jan 2016. URL: https://doi.org/10.1186/s13568-015-0169-5, doi:10.1186/s13568-015-0169-5. This article has 17 citations and is from a peer-reviewed journal.
(yamamoto2016synergisticpropertiesof pages 4-5): Kosuke Yamamoto and Yutaka Tamaru. Synergistic properties of cellulases from clostridium cellulovorans in the presence of cellobiose. AMB Express, Jan 2016. URL: https://doi.org/10.1186/s13568-015-0169-5, doi:10.1186/s13568-015-0169-5. This article has 17 citations and is from a peer-reviewed journal.
(cai2000analysisofcellulolytic pages 21-27): J Cai. Analysis of cellulolytic activities of chimeric proteins from clostridium cellulovorans. Unknown journal, 2000.
id: Q9RGE8
gene_symbol: engK
product_type: PROTEIN
status: DRAFT
taxon:
id: NCBITaxon:1493
label: Clostridium cellulovorans
description: >-
EngK is a glycoside hydrolase family 9 (GH9) endoglucanase from the Clostridium
cellulovorans cellulosome. It contains an N-terminal signal peptide, a GH9 catalytic
domain, a CBM4 carbohydrate-binding module, and a C-terminal type I dockerin domain
for cellulosome assembly. EngK catalyzes endo-1,4-β-glucanase activity, cleaving
internal β-1,4-glycosidic bonds in cellulose to produce primarily cellobiose. It
synergizes with the GH48 exoglucanase ExgS for efficient cellulose hydrolysis and
shows reduced sensitivity to cellobiose inhibition compared to EngH.
aliases:
- endoglucanase K
- glucanase
existing_annotations:
- term:
id: GO:0000272
label: polysaccharide catabolic process
evidence_type: IEA
original_reference_id: GO_REF:0000120
review:
summary: >-
This annotation is correct. EngK is an endoglucanase that directly participates
in polysaccharide (cellulose) catabolism by hydrolyzing β-1,4-glycosidic bonds.
action: ACCEPT
reason: >-
As a GH9 endoglucanase, EngK directly catalyzes the breakdown of polysaccharides.
This is a core function supported by biochemical characterization.
supported_by:
- reference_id: file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
supporting_text: "Biochemical assays of recombinant EngK from C. cellulovorans
demonstrate endo-1,4-β-glucanase activity"
- 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 correct but generic. EngK has hydrolase activity on
O-glycosyl bonds. More specific terms like GO:0008810 (cellulase activity)
better capture its function.
action: KEEP_AS_NON_CORE
reason: >-
This is a true parent term of the more specific cellulase activity. It's
correct but not the most informative annotation for this enzyme.
supported_by:
- reference_id: file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
supporting_text: "GH9 endoglucanases are modular cellulases that cleave
internal β-1,4-glycosidic bonds of cellulose"
- term:
id: GO:0005975
label: carbohydrate metabolic process
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: >-
This annotation is too general. EngK participates in cellulose catabolism
specifically, not general carbohydrate metabolism. More specific terms exist.
action: MARK_AS_OVER_ANNOTATED
reason: >-
This parent term is overly broad. GO:0030245 (cellulose catabolic process)
is the appropriate specific term for EngK function.
supported_by:
- reference_id: file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
supporting_text: "GH9 endoglucanases are modular cellulases that cleave
internal β-1,4-glycosidic bonds of cellulose"
- term:
id: GO:0008810
label: cellulase activity
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: >-
This annotation is correct and represents a core molecular function of EngK.
As a GH9 endoglucanase, EngK has cellulase activity that hydrolyzes cellulose.
action: ACCEPT
reason: >-
EngK is a GH9 family cellulase with demonstrated endo-1,4-β-glucanase activity.
This is the appropriate molecular function annotation.
supported_by:
- reference_id: file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
supporting_text: "Biochemical assays of recombinant EngK from C. cellulovorans
demonstrate endo-1,4-β-glucanase activity that yields predominantly cellobiose"
- term:
id: GO:0016787
label: hydrolase activity
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: >-
This annotation is too general. EngK has hydrolase activity, but more specific
terms like cellulase activity better describe its function.
action: MARK_AS_OVER_ANNOTATED
reason: >-
This is a very broad parent term. GO:0008810 (cellulase activity) is the
appropriate level of specificity for this GH9 enzyme.
supported_by:
- reference_id: file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
supporting_text: "GH9 family endoglucanase"
- term:
id: GO:0016798
label: hydrolase activity, acting on glycosyl bonds
evidence_type: IEA
original_reference_id: GO_REF:0000120
review:
summary: >-
This annotation is correct but not as specific as GO:0008810. EngK acts
on glycosyl bonds in cellulose.
action: KEEP_AS_NON_CORE
reason: >-
This is a parent term of cellulase activity. It's correct but less informative
than the more specific GO:0008810 annotation.
supported_by:
- reference_id: file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
supporting_text: "cleave internal β-1,4-glycosidic bonds of cellulose"
- term:
id: GO:0030245
label: cellulose catabolic process
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: >-
This annotation is correct and represents the core biological process for
EngK.
As an endoglucanase, EngK directly participates in cellulose degradation.
action: ACCEPT
reason: >-
EngK is a cellulosomal endoglucanase that catalyzes cellulose hydrolysis.
This is the appropriate biological process annotation.
supported_by:
- reference_id: file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
supporting_text: "EngK is a GH9 family endoglucanase from Clostridium cellulovorans;
described as a cellulosomal subunit"
# NEW ANNOTATIONS
- term:
id: GO:0043263
label: cellulosome
evidence_type: TAS
original_reference_id: file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
review:
summary: >-
EngK is a cellulosomal enzyme that assembles into the cellulosome via its
dockerin domain. This cellular component annotation is essential.
action: NEW
reason: >-
EngK contains a type I dockerin domain and was identified as a cellulosomal
subunit by cohesin-affinity profiling.
supported_by:
- reference_id: file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
supporting_text: "EngK detected as dockerin-bearing (thus cellulosomal)"
- term:
id: GO:0005576
label: extracellular region
evidence_type: TAS
original_reference_id: file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
review:
summary: >-
EngK is secreted and functions extracellularly as part of the cellulosome.
It has a signal peptide for secretion.
action: NEW
reason: >-
EngK contains a signal peptide (residues 1-23) and is secreted to function
in the extracellular cellulosome complex.
supported_by:
- reference_id: file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
supporting_text: "EngK is secreted and incorporated into extracellular cellulosome
complexes via its dockerin domain"
- term:
id: GO:1990311
label: type-I cohesin domain binding
evidence_type: TAS
original_reference_id: file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
review:
summary: >-
EngK contains a type I dockerin domain that binds to type I cohesins on the
CbpA scaffoldin, enabling cellulosome assembly.
action: NEW
reason: >-
The dockerin domain mediates binding to cohesin domains, which is essential
for cellulosome incorporation.
supported_by:
- reference_id: file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
supporting_text: "C-terminal dockerin (cellulosome-targeting)"
- term:
id: GO:0044575
label: cellulosome assembly
evidence_type: NAS
review:
summary: Added to align core_functions with existing annotations.
action: NEW
reason: Core function term not present in existing_annotations.
references:
- id: GO_REF:0000002
title: Gene Ontology annotation through association of InterPro records with
GO terms
findings: []
- id: GO_REF:0000043
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword
mapping
findings: []
- id: GO_REF:0000120
title: Combined Automated Annotation using Multiple IEA Methods
findings: []
- id: file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
title: Deep research summary for Q9RGE8/engK
findings:
- statement: EngK is a GH9 family endoglucanase with cellulase activity
supporting_text: "Biochemical assays of recombinant EngK from C. cellulovorans
demonstrate endo-1,4-β-glucanase activity"
- statement: EngK produces primarily cellobiose from cellulose
supporting_text: "products reported as primarily cellobiose and/or short oligos"
- statement: EngK synergizes with ExgS exoglucanase
supporting_text: "EngK synergizes with the GH48 exoglucanase ExgS on acid-swollen
cellulose"
core_functions:
- description: >-
EngK is a GH9 endoglucanase that catalyzes the hydrolysis of β-1,4-glycosidic
bonds in cellulose, producing primarily cellobiose. It functions as part of
the cellulosome to efficiently degrade plant cell wall polysaccharides.
molecular_function:
id: GO:0008810
label: cellulase activity
directly_involved_in:
- id: GO:0030245
label: cellulose catabolic process
locations:
- id: GO:0005576
label: extracellular region
in_complex:
id: GO:0043263
label: cellulosome
supported_by:
- reference_id: file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
supporting_text: "Biochemical assays of recombinant EngK from C. cellulovorans
demonstrate endo-1,4-β-glucanase activity"
- description: >-
EngK contains a type I dockerin domain that binds to cohesins on the CbpA
scaffoldin, enabling its incorporation into the cellulosome complex.
molecular_function:
id: GO:1990311
label: type-I cohesin domain binding
directly_involved_in:
- id: GO:0044575
label: cellulosome assembly
locations:
- id: GO:0005576
label: extracellular region
in_complex:
id: GO:0043263
label: cellulosome
supported_by:
- reference_id: file:CLOCL/Q9RGE8/Q9RGE8-deep-research-falcon.md
supporting_text: "EngK detected as dockerin-bearing (thus cellulosomal)"
proposed_new_terms: []
suggested_questions:
- question: >-
What is the structural basis for EngK's reduced sensitivity to cellobiose
inhibition compared to EngH?
experts: []
suggested_experiments:
- description: >-
Detailed kinetic characterization of EngK on various cellulose substrates
to determine Km, kcat, and product profile.
hypothesis: >-
EngK may have a distinct active site architecture that favors cellobiose
release and reduces product inhibition.