Distribution of .OMEGA.-amino acid: Pyruvate transaminase and aminobutyrate: .ALPHA.-Ketoglutarate transaminase in microorganisms.

Abstract

The distribution of ω-ammo acid transaminases in microorganisms was investigated. ω-Amino acid : pyruvate t ansaminase (ω-APT) was found bacteria and yeasts, but not in actinomycetes and fungi. On the contrary, aminobutyrate : α-ketoglutarate transaminase (GABA-T) was shown in most of the microorganisms from bacteria to fungi. β-Alanine is a preferred amino donor for the ω-APT reaction. Although bacterial and yeast GABA-T are inactive for β-alanine, fungal and actinomycete enzymes react with this compound and γ-aminobutyrate. In comparing these results with those of plant and mammalian enzymes, two different pathways of ω-amino acid metabolism are suggested for bacteria, yeast and plants, i.e. one for β-alanine and the other for γ-aminobutyrate, catalyzed by ω-APT and GABA-T, respectively. In actinomycetes, fungi, and mammals GABA-T may be involved in the metabolism of both ω-amino acids. In addition, evolutionary changes of ω-amino acid transaminases are discussed.