PURIFICATION AND PROPERTIES OF L-ORNITHINE DELTA-AMINOTRANSFERASE FROM GRAMICIDIN S-PRODUCING BACILLUS-BREVIS

In gramicidin S-producing Bacillus brevis, the addition of L-ornithine to the minimal medium with L-glutamate as the sole carbon and nitroge n source caused an 8-fold induction of L-ornithine delta-aminotransfer ase [EC2.6.1.13]. The enzyme was purified to homogeneity. The native e nzyme had a molecular weight of about 88,000 after gel filtration and consisted of two subunits with an identical in molecular weight of abo ut 45,000. The enzyme was specific for L-ornithine (K-m = 1.05 mM) as an amino donor and for 2-oxoglutarate (K-m = 6.25 mM) as an amino acce ptor, and catalyzed the conversion of L-ornithine and 2-oxoglutarate, respectively, to glutamic-gamma-semialdehyde, which is spontaneously c yclized to Delta(1)-pyrroline-5-carboxylate and L-glutamate. The enzym e exhibits an absorption maximum at 425 nm at neutral pH, and 1 mol of pyridoxal phosphate is bound per subunit. The enzyme activity was irr eversibly inhibited by gabaculine, and L-ornithine protected the enzym e from the inhibition. The N-terminal amino acid sequence revealed a n oteworthy similarity between human and yeast L-ornithine delta-aminotr ansferases in residues 17-28 of the B. brevis enzyme.