Open AccessEffects of Alcohols on β‐Galactosidase‐Catalyzed Hydrolysis of n ‐Alkyl‐β‐ d ‐galactopyranosides
Author(s) -
Groen Guido,
WoutersLeysen Josée,
Yde Marc,
De Bruyne Clemens K.
Publication year - 1973
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1973.tb03041.x
Subject(s) - chemistry , nucleophile , alkyl , hydrolysis , enzyme , galactosides , stereochemistry , reactivity (psychology) , catalysis , aryl , medicinal chemistry , organic chemistry , medicine , alternative medicine , pathology
The effect of an homologous series of n ‐alkyl β‐ d ‐galactopyranosides on the enzymic activity of β‐ d ‐galactosidase from Escherichia coli ML 309 was investigated. The affinity of the enzyme for these substrates increases with the length of the apolar chain, indicating that the aglycon is bound through hydrophobic forces. Addition of alcohols as nucleophilic competitors indicates that the reaction of aryl and alkyl β‐ d ‐galactosides proceeds via a common galactosyl·enzyme intermediate, whose formation is rate‐limiting. The reactivity of the alcohols cannot be explained merely in terms of their relative nucleophilicity. It is necessary to assume that the alcohols interact with the enzyme to form adsorptive complexes, and that the conformation of the enzyme changes during the formation of the enzyme·galactosyl complex. Alcohols also function as competitive inhibitors by binding to the free enzyme.