Pyridoxamine-pyruvate transaminase. 1. Determination of the active site stoichiometry and the pH dependence of the dissociation constant for 5'-deoxypyridoxal.

Spectrophotometric titration of pyridoxamine-pyruvate transaminase (EC 2.6.1.30) with pyridoxal at pH 7.15 gives four equivalent binding sites per tetramer. The pH dependence of the equilibrium constant for the association of 5'-deoxypyridoxal with the active site lysine residue was determined spectrophotometrically. These dissociation constants increase… (More)