Oxygenase side reactions of acetolactate synthase and other carbanion-forming enzymes.

摘要: Enzymes that mediate carbanion chemistry must protect their reactants from solvent and undesirable electrophiles, such as molecular oxygen. A number of enzymes utilize carbanionic in- termediates were surveyed for 02-consuming side reactions. Several these enzymes, acetolactate synthase, pyruvate decarboxylase, class I1 aldolase, glutamate catalyze previously undetected oxygen-consuming reactions, while others I ( (phosphoribosyl)amino) imidazole carboxylase, 6-phosphogluconate dehydrogenase, iswitrate triosephosphate isomerase do not. Prior to this work, only ribulosebisphosphate carboxylase was known an oxygenase reaction. These new examples indicate reactions are a more general feature enzyme-mediated than has been appreciated, they not necessarily inevitable consequence chemistry. Expression activity depends on the accessibility intermediate oxygen but also may depend ability enzyme stabilize initially formed peroxide anion either through protonation with appropriate enzymic group or metal coordination.