Bromopyruvate inactivation of glutamate apodecarboxylase. Kinetics and specificity.

摘要: A number of halo carboxylic and dicarboxylic acids were substrate-competitive inhibitors glutamate decarboxylase, with bromosuccinate, 3-bromopropionate, iodoacetate having the highest affinity for enzyme. Some also inactivated apoenzyme. Bromopyruvate at relatively low concentrations apoenzyme irreversibly. The rate inactivation apodecarboxylase was proportional to bromopyruvate concentration approached a constant high concentration. These data are consistent two-step process in which an enzyme-bromopyruvate complex is formed followed by inactivation. giving half-maximum 6.9 mM, maximum 1.75 min-1 pH 4.6 23 degrees. Much faster rates obtained 5.96 6.44. Phosphate, inhibitor pyrisoxal-P binding apoenzyme, competitively inhibited bromopyruvate. In addition, pyridoxal-P Kinetics incorporation bromo[2-14C]pyruvate indicated that complete when 1.2 mol radioactive residue covalently bound per subunit Amino acid analyses demonstrated cysteinyl alkylated evidently interacting nincovalently cationic group or near pyridoxal-P-binding site, then alkylating nearby residue.