Purification and properties of the aromatic amino acid aminotransferase from gramicidin S-producing Bacillus brevis

Abstract

The aromatic amino acid aminotransferase was purified to a homogenous state from a gramicidin S-producing strain of Bacillus brevis. The enzyme shows a molecular weight of about 71,000 on gel-filtration. The subunit molecular weight is about 35,000 as determined by sodium dodecyl sulfate gel electrophoresis, indicating that the enzyme is a dimer. The enzyme exhibits absorption maxima near 425 and 330 nm at neutral pH. One mole of pyridoxal phosphate is bound per subunit. The enzyme has amino donor specificity for aromatic amino acids, L-phenylalanine, L-tyrosine, and L-tryptophan, and utilizes 2-oxoglutarate as the amino acceptor. This enzyme activity was separated from both the aspartate aminotransferase activity and the branched chain amino acid aminotransferase activity by chromatography on DEAE-Sephadex.