Catalytic consequences of experimental evolution. Part 2. Rate-limiting degalactosylation in the hydrolysis of aryl β-D-galactopyranosides by the experimental evolvants ebga and ebgb

Abstract

The build-up of a galactosyl-enzyme intermediate in the hydrolysis of 2-naphthylgalactoside by ebg^b enzyme has been observed by fluorescence in a stopped-flow apparatus. Degalactosylation has been shown to be rate limiting in the steady-state hydrolysis of 3,4-dinitrophenylgalactoside by both ebg^a and ebg^b enzymes by nucleophilic competition with methanol. The implications of this slowing down of degalactosylation as a consequence of experimental evolution of the gene are discussed.