Affinity Labeling of Aspartate Aminotransferase Isozymes by Bromopyruvate

摘要: Abstract Incubation with bromopyruvate did not cause appreciable inactivation of either supernatant or mitochondrial isozyme aspartate aminotransferase from pig heart. In the presence l-cysteine sulfinate l-aspartate, however, rapidly inactivated both isozymes. Bromopyruvate also acted as a keto acid substrate in conversion pyridoxamine form enzymes to their pyridoxal forms. This finding, together demonstration equimolar formation oxalacetate, pyruvate, and ammonia l-aspartate bromopyruvate, supported following reaction sequences: [see PDF for equation] where Em is El these enzymes. A kinetic study reactions revealed that occurs during Reaction I. Spectral chemical analyses showed coenzyme present phosphate carbon 3 moiety covalently bound enzyme active sites. finding indicates an efficient affinity label each isozyme. Kinetics incorporation bromo[2-14C]pyruvate modified amino residues demonstrated resulted alkylation essential cysteinyl residue region by bromopyruvate.