Submitted to: American Chemical Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: March 29, 2007
Publication Date: March 29, 2007
Citation: Jordan, D.B. 2007. Structure-function relationships of a catalytically efficient beta-D-xylosidase [abstract]. American Chemical Society. Paper No. 175. Technical Abstract: Beta-D-xylosidase from Selenomonas ruminantium has been revealed as the best catalyst known for promoting hydrolysis of 1,4-beta-D-xylooligosaccharides, and it has potential utility in saccharification processes. Kinetic parameters, kcat and kcat/Km, are more than 10-fold larger than those reported for the enzyme isolated from other organisms. In cleaving 1,4 glycosidic bonds, the family 43 glycoside hydrolase acts through an inversion mechanism and cleaves a single xylose residue from the nonreducing end of xylooligosaccharides per catalytic cycle without processivity. Three-dimensional structures of homologous GH43 xylosidases indicate that the enzyme active site has only two subsites for recognition of substrate, the two terminal xylosyl residues that share the sessile glycosidic bond. The pKa values of the catalytic acid (~7) and catalytic base (~5) and the two subsites of the active site are key components to a kinetic model that accounts for catalytic properties such as substrate specificities, inhibitor binding, and influences of pH.