Polyanionic inhibitors of phosphoglycerate mutase: Combined structural andbiochemical analysis

The effects that the inhibitors inositol hexakisphosphate and benzene tri-, tetra- and hexacarboxylates have on the phosphoglycerate mutases from Sacc haromyces cerevisiae and Schizosaccharomyces pombe have been determined. Th eir Ki values have been calculated, and the ability of the inhibitors to pr otect the enzymes against limited proteolysis investigated. These biochemic al data have been placed in a structural context by the solution of the cry stal structures of S. cerevisiae phosphoglycerate mutase soaked with inosit ol hexakisphosphate or benzene hexacarboxylate. These large polyanionic com pounds bind to the enzyme so as to block the entrance to the active-site cl eft. They form multiple interactions with the enzyme, consistent with their low Ki values, and afford good protection against limited proteolysis of t he C-terminal region by thermolysin. The inositol compound is more efficaci ous because of its greater number of negative charges. The S. pombe phospho glycerate mutase that is inherently lacking a comparable C-terminal region has higher Ki values for the compounds tested. Moreover, the S. pombe enzym e is less sensititive to proteolysis, and the presence or absence of the in hibitor molecules has little effect on susceptibility to proteolysis. (C) 1 999 Academic Press.