Stereochemistry of reactions catalyzed by glutamate decarboxylase

Abstract

When the decarboxylation of L-glutamic acid by the glutamate decarboxylase [EC 4.1.1.15] from Escherichia coli is carried out in D2O [deuterium oxide], the product .gamma.-aminobutyric acid contains a single deuterium atom. The stereochemistry of this material was established by conversion to levorotatory methyl 4-phthalimido[4-2H]butyrate. The dextrorotatory isomer of the latter compound was synthesized from S-[2-2H]glycine by a series of reactions not affecting the stereochemistry at the chiral center. Thus, the decarboxylation of glutamic acid occurs with retention of configuration. Decarboxylation of L-.alpha.-methylglutamic acid by this enzyme produces levorotatory .gamma.-aminovaleric acid and thus also occurs with retention of configuration.