The mechanism of the reaction catalyzed by uronate isomerase illustrates how an isomerase may have evolved from a hydrolase within the amidohydrolase superfamily.

ABSTRACT: Uronate isomerase (URI) catalyzes the reversible isomerization of D-glucuronate to D-fructuronate and of D-galacturonate to D-tagaturonate. URI is a member of the amidohydrolase superfamily (AHS), a highly divergent group of enzymes that catalyze primarily hydrolytic reactions. The chemical mechanism and active site structure of URI were investigated in an attempt to improve our understanding of how an active site template that apparently evolved to catalyze hydrolytic reactions has been reforged to catalyze an isomerization reaction. The pH-rate profiles for k(cat) and k(cat)/K(m) for URI from Escherichia coli are bell-shaped and indicate that one group must be unprotonated and another residue must be protonated for catalytic activity. Primary isotope effects on the kinetic constants with

SUBMITTER: Nguyen TT 

PROVIDER: S-EPMC2773443 | biostudies-literature | 2009 Sep

REPOSITORIES: biostudies-literature