2xyl
From Proteopedia
CELLULOMONAS FIMI XYLANASE/CELLULASE COMPLEXED WITH 2-DEOXY-2-FLUORO-XYLOBIOSE
Structural highlights
FunctionGUX_CELFI Hydrolyzes both cellulose and xylan. Has also weak endoglucanase activity. The biological conversion of cellulose to glucose generally requires three types of hydrolytic enzymes: (1) Endoglucanases which cut internal beta-1,4-glucosidic bonds; (2) Exocellobiohydrolases that cut the dissaccharide cellobiose from the non-reducing end of the cellulose polymer chain; (3) Beta-1,4-glucosidases which hydrolyze the cellobiose and other short cello-oligosaccharides to glucose. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe retaining beta-1,4-glycanase Cex from Cellulomonas fimi, a family 10 glycosyl hydrolase, hydrolyzes xylan 40-fold more efficiently than cellulose. To gain insight into the nature of its preference for xylan, we determined the crystal structure of the Cex catalytic domain (Cex-cd) trapped as its covalent 2-deoxy-2-fluoroxylobiosyl-enzyme intermediate to 1.9 A resolution. Together with the crystal structure of unliganded Cex-cd [White, A., et al. (1994) Biochemistry 33, 12546-12552] and the previously determined crystal structure of the covalent 2-deoxy-2-fluorocellobiosyl-Cex-cd intermediate [White, A., et al. (1996) Nat. Struct. Biol. 3, 149-154], this structure provides a convincing rationale for the observed substrate specificity in Cex. Two active site residues, Gln87 and Trp281, are found to sterically hinder the binding of glucosides and must rearrange to accommodate these substrates. Such rearrangements are not necessary for the binding of xylobiosides. The importance of this observation was tested by examining the catalytic behavior of the enzyme with Gln87 mutated to Met. This mutation had no measurable effect on substrate affinity or turnover number relative to the wild type enzyme, indicating that the Met side chain could accommodate the glucoside moiety as effectively as the wild type Gln residue. Subsequent mutagenesis studies will address the role of entropic versus enthalpic contributions to binding by introducing side chains that might be more rigid in the unliganded enzyme. Exploring the cellulose/xylan specificity of the beta-1,4-glycanase cex from Cellulomonas fimi through crystallography and mutation.,Notenboom V, Birsan C, Warren RA, Withers SG, Rose DR Biochemistry. 1998 Apr 7;37(14):4751-8. PMID:9537990[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
| ||||||||||||||||||||
