Stereochemistry of the reaction catalysed by glutamic acid decarboxylase from a higher plant ( Hordeum vulgare)

The decarboxylation of (2S)-glutamic acid to yield γ-aminobutyric acid catalysed by L-glutamic acid decarboxylase (EC 4.1.1.15) from Hordeum vulgare proceeds with net retention. The result is interpreted in terms of a single progenitor hypothesis of the pyridoxal phosphate enzymes and confirms that not only bacteria and animals but also plant decarboxylases catalyse the biosynthesis of biogenic amines from amino acids with net retention.