642-93-3Relevant articles and documents
Pyridoxamine and 2-Oxalopropionic Acid in Aqueous Systems: Conditional Imine Formation Constants and Rate Constants of Vitamin B6 Catalyzed Decarboxylation
Kubala, Gregory,Martell, Arthur E.
, p. 449 - 455 (1983)
The conditional Schiff base formation constants (Kc) of pyridoxamine (PM) and 2-oxalopropionic acid (OPA) were determined spectrophotometrically in basis aqueous solutions.These equilibrium constants exhibit pH dependence with maximum ketimine formation occuring near pH 9.0 (Kc = 9.6).The kinetics of vitamin B6 catalyzed decarboxylation of OPA have been studied spectrophometrically, and the observed rate constant of decarboxylation (kobsd) exhibited pH dependence with the maximum occuring at approximatly the pH corresponding to maximum ketimine formation (kobsd = 15.6 * 10-4 s-1 at 1.01 * 10-4 M OPA and 1.00 * 10-5 M PM).Microscopic rate constants (kSB) for the decarboxylation of the Schiff base species present in solution also showed pH dependence with the greatest catalytic activity at pH 7.0 (kSB = 38.4 s-1) and the least at pH 12.47 (kSB = 0.2 s-1).The relative magnitudes of the kSB's determined are discussed in terms of the various protonated forms of the OPA:PM ketimine,and the corresponding pKa's have been estimated from the rate constant-pH profiles.
