Abstract
The enzymatic degradation of cellulose, by cellulases, is not only industrially important in the food, paper, and textile industries but also a potentially useful method for the environmentally friendly recycling of municipal waste, An understanding of the structural and mechanistic requirements for the hydrolysis of the beta-1,4 glycosidic bonds of cellulose is an essential prerequisite for beneficial engineering of cellulases for these processes, Cellulases have been classified into 13 of the 62 glycoside hydrolase families [Henrissat, B., and Bairoch, A. (1996) Biochem J. 316, 695-696]. The structure of the catalytic core of the family 5 endoglucanase, Ce15A, from the alkalophilic Bacillus agaradherans has been solved by multiple isomorphous replacement at 1.6 Angstrom resolution. Cel5A has the (alpha/beta)(8) barrel structure and signature structural features typical of the grouping of glycoside hydrolase families known as dan GH-A, with the catalytic acid/base Glu 139 and nudeophile Glu 228 on barrel strands beta 4 and beta 7 as expected, In addition to the native enzyme, the 2.0 Angstrom resolution structure of the cellobiose-bound form of the enzyme has also been determined, Cellobiose binds preferentially in the -2 and -3 subsites of the enzyme. Kinetic studies on the isolated catalytic core domain of Cel5A, using a series of reduced cellodextrins as substrates, suggest approximately five to six binding sites, consistent with the shape and size of the cleft observed by crystallography.
| Original language | English |
|---|---|
| Pages (from-to) | 1926-1932 |
| Number of pages | 7 |
| Journal | Biochemistry |
| Volume | 37 |
| Issue number | 7 |
| Publication status | Published - 17 Feb 1998 |
Keywords
- ACID-SEQUENCE SIMILARITIES
- FREE R-VALUE
- CRYSTAL-STRUCTURE
- GLYCOSYL HYDROLASES
- BETA-GLUCOSIDASE
- 3-DIMENSIONAL STRUCTURE
- CELLULOMONAS-FIMI
- CATALYTIC DOMAIN
- PROTEIN MODELS
- ACTIVE-SITE