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Glycoside Hydrolase Family 6

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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.



Table. Putative catalytic residues of some representatives in GH family 6
(with biochemical characterization of wt and mutant enzymes).
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

  1. 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

    [Knowles1988]
  2. 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 | PubMed ID:8755548 [Kuhls1996]
  3. 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 | PubMed ID:2377893 [Rouvinen1990]
  4. 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 | PubMed ID:8399160 [Spezio1993]

All Medline abstracts: PubMed