Hydrolyses of alpha- and beta-cellobiosyl fluorides by cellobiohydrolases of Trichoderma reesei.
Biochem J
; 291 ( Pt 3): 883-8, 1993 May 01.
Article
in En
| MEDLINE
| ID: mdl-8489514
ABSTRACT
Cellobiohydrolase II hydrolyses alpha- and beta-D-cellobiosyl fluorides to alpha-cellobiose at comparable rates, according to Michaelis-Menten kinetics. The stereochemistry, absence of transfer products and strict hyperbolic kinetics of the hydrolysis of alpha-cellobiosyl fluoride suggest that the mechanism for the alpha-fluoride may be the enzymic counterpart of the SNi reaction observed in the trifluoroethanolysis of alpha-glucopyranosyl fluoride [Sinnott and Jencks (1980) J. Am. Chem. Soc. 102, 2026-2032]. The absolute factors by which this enzyme accelerates fluoride ion release are small and greater for the alpha-fluoride than for the beta, suggesting that its biological function may not be just glycoside hydrolysis. Cellobiohydrolase I hydrolyses only beta-cellobiosyl fluoride, which is, however, an approx. 1-3% contaminant in alpha-cellobiosyl fluoride as prepared and purified by conventional methods. Instrumental assays for the various components of the cellulase complex are discussed.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Trichoderma
/
Cellobiose
/
Glycoside Hydrolases
Language:
En
Journal:
Biochem J
Year:
1993
Document type:
Article