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Glycoside Hydrolase Family 6
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- Author: ^^^Kathleen Piens^^^ and ^^^Gideon Davies^^^
- Responsible Curator: ^^^Gideon Davies^^^
| Glycoside Hydrolase Family GH6 | |
| Clan | none |
| Mechanism | inverting |
| Active site residues | acid known, base debated |
| CAZy DB link | |
| http://www.cazy.org/fam/GH6.html | |
Substrate specificities
Glycoside hydrolases of family 6 cleave β-1,4 glycosidic bonds in cellulose/β-1,4-glucans. Only endoglucanase (EC 3.2.1.4) and cellobiohydrolase (EC 3.2.1.91) activity has been reported for both bacterial and eukaryotic members of this family.
Kinetics and Mechanism
Family 6 enzymes are inverting enzymes, as first shown by NMR [1] on Cellobiohydrolase II (CBH II; Cel6A) from the fungus Trichoderma reesei (a clonal derivative of Hypocrea jecorina [2]).
Catalytic Residues
Content is to be added here.
| Proposed role | CfCel6A (endo) | HiCel6A (exo) | HjCel6A (exo) | TfCel6A (endo) | TfCel6B (exo) |
|---|---|---|---|---|---|
| Substrate distortion | Asp210 | Tyr174 | Tyr169 | Tyr73 | Tyr220 |
| Increase in pKa acid/Catalytic base | Asp216 | Asp180 | Asp175 | Asp79 | Asp226 |
| Proton network | Gly222 | Ser186 | Ser181 | Ser85 | Asp232 |
| Catalytic acid | Asp252 | Asp226 | Asp221 | Asp117 | Asp274 |
| Catalytic base/substrate binding | Asp392 | Asp405 | Asp401 | Asp265 | Asp497 |
Three-dimensional structures
Content is to be added here.
Family Firsts
- First sterochemistry determination
- Cite some reference here, with a short (1-2 senetence) explanation.
- First general acid/base residue identification
- Cite some reference here, with a short (1-2 senetence) explanation.
- First 3-D structure
- The catalytic core domain of the Trichoderma reesei (the organism now known as Hypocrea jecorina) cellobiohydrolase II by the Jones group [3]. The first endoglucanase in this family was the Thermomonospora fusca E2 enzyme (catalytic core) solved by the Wilson/Karplus groups[4]
References
-
Knowles, J.K.C., Lehtovaara, P., Murray, M. and Sinnott, M.L. (1988) Stereochemical course of the action of the cellobioside hydrolases I and II of Trichoderma reesei. J. Chem. Soc., Chem. Commun., 1988, 1401-1402. DOI: 10.1039/C39880001401
- Kuhls K, Lieckfeldt E, Samuels GJ, Kovacs W, Meyer W, Petrini O, Gams W, Börner T, and Kubicek CP. (1996). Molecular evidence that the asexual industrial fungus Trichoderma reesei is a clonal derivative of the ascomycete Hypocrea jecorina. Proc Natl Acad Sci U S A. 1996;93(15):7755-60. DOI:10.1073/pnas.93.15.7755 |
- Rouvinen J, Bergfors T, Teeri T, Knowles JK, and Jones TA. (1990). Three-dimensional structure of cellobiohydrolase II from Trichoderma reesei. Science. 1990;249(4967):380-6. DOI:10.1126/science.2377893 |
- Spezio M, Wilson DB, and Karplus PA. (1993). Crystal structure of the catalytic domain of a thermophilic endocellulase. Biochemistry. 1993;32(38):9906-16. DOI:10.1021/bi00089a006 |