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-Ξ²-glucanase activity, cleaving internal Ξ²-1,4-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 Ξ²-1,4-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-Ξ²-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 Ξ²-1,4-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 Ξ²-1,4-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-Ξ²-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-Ξ²-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 Ξ²-1,4-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. |
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Download this section (compressed HTML)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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