DIALKYLGLYCINE DECARBOXYLASE STRUCTURE - BIFUNCTIONAL ACTIVE-SITE ANDALKALI-METAL SITES

The structure of the bifunctional, pyridoxal phosphate-dependent enzym e dialkylglycine decarboxylase was determined to 2.1-angstrom resoluti on. Model building suggests that a single cleavage site catalyzes both decarboxylation and transamination by maximizing stereoelectronic adv antages and providing electrostatic and general base catalysis. The en zyme contains two binding sites for alkali metal ions. One is located near the active site and accounts for the dependence of activity on po tassium ions. The other is located at the carboxyl terminus of an alph a helix. These sites help show how proteins can specifically bind alka li metals and how these ions can exert functional effects.