Non-enzymatic transamination and β-elimination of DL-S-benzylcysteine catalysed by a potent pyridoxal model

Abstract

Non-enzymatic reactions of DL-S-benzylcysteine (2_H) promoted by N-dodecylpyridoxal (1a) have been investigated in an aqueous hexadecyltrimethylammonium chloride (CTACI) micelle at 30.0 °C. The substrate undergoes mainly β-elimination at alkaline pH, whereas transamination with (1a) predominates in weakly acidic media. The kinetic α-deuterium isotope effects (k_H/k_D) of substrate were determined as 8.7 and 5.5 for β-elimination and transamination, respectively, at pH 7.0. These data indicate unambiguously that the rate-determining step of both reactions is the α-hydrogen abstraction from the reactive Schiff's base of substrate and (1a).