The three-dimensional structure of omega-amino acid:pyruvate aminotransferase from Pseudomonas sp. F-126, an isologous alpha 4 tetramer containing pyridoxal 5'-phosphate (PLP) as a cofactor, has been determined at 2.0 A resolution. The diffraction data were collected with a newly developed Weissenberg camera with a Fuji Imaging Plate, using synchrotron radiation. The mean figure-of-merit was 0.57. The subunit is rich in secondary structure and comprises two domains. PLP is located in the large domain. The high homology in the secondary structure between this enzyme and aspartate aminotransferase strongly indicates that these two types of enzymes have evolved from a common ancestor.

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Succinic semialdehyde -FL-Glutamate 13-alanine transaminase is characterized by its requirement for pyruvate and r-aminobutyrate transaminase for a-ketoglutarate as an amino acceptor. With the latter enzyme, many studies have been carried out using mammalian enzyme with an emphasis on its physiological function.8-10) Some of them were purified to homogeneity and partially characterized. There are another (0-amino acid transaminase catalyzing transamination of co-amino group of a, w-diaminocarboxylic acid such as C6 of L-lysine and C5 of L-ornithine, which were purified and crystallized from bacteria. These enzymes, however, do not catalyze the transamination of r-aminobutyrate or p-alanine. Taurine : a-ketoglutarate aminotransferase catalyzing transamination of (0-amino acids besides that of taurine was also purified and crystallized from Achromobacter superficialis.13) Recently, we purified and crystallized co-amino acid: pyruvate and r-aminobutyrate : a-ketoglutarate aminotransferase from Pseudomonas sp. F-126, which enabled us to characterize the enzymologic properties in detail.14-18) In this review we will try briefly to present and discuss some properties of the (0-amino acid transaminase in comparison with other transaminases, especially r-aminobutyrate transaminase.co-Amino acid : pyruvate aminotransferase designated previously taurine : pyruvate aminotransferase14) can be classified as p-alanine : pyruvate aminotransferase (E.C. 2.6.1.18). The terminology, however, of "w-amino acid: pyruvate aminotransferase" is more relevant from the view point of its substrate specificity as described below.

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The stereospecific removal of the 4-fWo-8hydrogen of y-aminobutyrate (GABA) has been demonstrated with a bacterial w-amino acid : pyruvate aminotransferase, while stereospecific removal of the 4-pro-Shydrogen has been demonstrated with a-oxoglutarate requiring bacterial GA4BA transsminase.