Transamination of γ-aminobutyric acid; a semiempirical molecular orbital study of the transaminase mechanism

Abstract

The mechanism of the pyridoxal-5-phosphate (PLP) dependent enzyme γ-aminobutyric acid aminotransferase (EC 2.6.1.19, GABA-T) was investigated using the AM1 semiempirical molecular orbital method. The atomic charges calculated for the isolated reaction intermediates and the differences in the HOMO and LUMO energy levels are consistent with the experimentally determined mechanism. To examine the role of the ring nitrogen, a pyridoxal analogue in which the pyridine ring nitrogen is replaced by CH is considered in the model reaction steps of the same enzyme.