SCHIFF-BASES OF PYRIDOXAL 5'-PHOSPHATE AND POLYPEPTIDES CONTAINING L-LYSINE - A KINETIC-STUDY

The apparent rate constants of formation (k1) and hydrolysis (k2), and the apparent equilibrium constant (K(pH)) of the Schiff bases of pyridoxal 5'-phosphate and poly-L-lysine in different degrees of polymerization have been determined as a function of pH at 25-degrees-C and a constant ionic strength of 0.1. The Schiff bases of PLP and L-lysine and L-alanine copolymers were also studied under the same conditions. The k1 and K(pH) values obtained in every instance were larger than those reported for Schiff bases of PLP and primary amines. The absorption bands of the Schiff bases formed coincided with those obtained for the Schiff bases of PLP and primary amines in low-polarity media. These facts reveal the occurrence of effects that cannot be ascribed to the solvent and that influence intramolecular acid-base catalysis in the formation of the Schiff bases examined.