Glycoside Hydrolase Family 7

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• Author: ^^^Jerry Stahlberg^^^
• Responsible Curator: ^^^Jerry Stahlberg^^^

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Glycoside Hydrolase Family 7
Clan	GH-B
Mechanism	retaining
Active site residues	known
CAZy DB link
http://www.cazy.org/fam/GH7.html

Substrate specificities

Most glycoside hydrolases of family 7 cleave β-1,4 glycosidic bonds in cellulose/β-1,4-glucans. Several members also show activity on xylan. The substrate specificities found in GH7 are: endo-1,4-β-glucanase (EC 3.2.1.4), [reducing end-acting] cellobiohydrolase (EC 3.2.1.-), chitosanase (EC 3.2.1.132) and endo-1,3-1,4-β-glucanase (EC 3.2.1.73).

Kinetics and Mechanism

Family 7 enzymes are retaining enzymes, as first shown by NMR [1] on Cellobiohydrolase I (CBH I; Cel7A) from the fungus Trichoderma reesei (a clonal derivative of Hypocrea jecorina).

Catalytic Residues

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Three-dimensional structures

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Family Firsts

First sterochemistry determination

Hypocrea jecorina cellobiohydrolase Cel7A by NMR [1].

First catalytic nucleophile identification

Cite some reference here, with a short (1-2 sentence) explanation [2].

First general acid/base residue identification

Cite some reference here, with a short (1-2 sentence) explanation [3].

First 3-D structure

First cellobiohydrolase was Hypocrea jecorina Cel7A (CBH I; PDB 1cel) [4]. First endo-1,4-β-glucanase was Endoglucanase I (EG I, Cel7B) from Fusarium oxysporum (PDB 1byh) [5], both by X-ray crystallography.

References

1. Jonathan K. C. 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

2. Sinnott, M.L. (1990) Catalytic mechanisms of enzymic glycosyl transfer. Chem. Rev. 90, 1171-1202. DOI: 10.1021/cr00105a006

3. He S and Withers SG. (1997). Assignment of sweet almond beta-glucosidase as a family 1 glycosidase and identification of its active site nucleophile. J Biol Chem. 1997;272(40):24864-7. DOI:10.1074/jbc.272.40.24864 |
4. Divne C, Ståhlberg J, Reinikainen T, Ruohonen L, Pettersson G, Knowles JK, Teeri TT, and Jones TA. (1994). The three-dimensional crystal structure of the catalytic core of cellobiohydrolase I from Trichoderma reesei. Science. 1994;265(5171):524-8. DOI:10.1126/science.8036495 |
5. Sulzenbacher G, Driguez H, Henrissat B, Schülein M, and Davies GJ. (1996). Structure of the Fusarium oxysporum endoglucanase I with a nonhydrolyzable substrate analogue: substrate distortion gives rise to the preferred axial orientation for the leaving group. Biochemistry. 1996;35(48):15280-7. DOI:10.1021/bi961946h |
6. Robert V. Stick and Spencer J. Williams. (2009) Carbohydrates. Elsevier Science.