Toshio Kimura

Purification and Characterization of γ-Glutamylmethylamide Synthetase from Methylophaga sp. AA-30.

γ-Glutamylmethylamide synthetase [L-glutamate: methylamine ligase (ADP-forming), EC 6.3.4.12] was purified about 70-fold from a cell-free extract of Methylophaga sp. AA-30 by ammonium sulfate fractionation, Octyl-Sepharose column chromatography, and Sephacryl S-300 gel filtration. Only a single protein band was detected after SDS-polyacrylamide gel electrophoresis of the purified preparation; the band was at a position corresponding to a molecular weight of 56,000. The molecular weight of the enzyme was calculated to be 440,000 by Superose 6HR gel filtration, so we suggest that the enzyme is an octomer of identical subunits. The enzyme had maximum activity at pH 7.5 and 40°C. It could use ethylamine and propylamine instead of methylamine as the substrate, but it could not use D-glutamate or L-glutamine instead of L-glutamate.

Studies on microbial population in coastal waters - V. Generic composition and physiological properties of nitrogen-scavenging bacteria isolated from marine environments.

Nitrogen-scavenging bacteria were isolated from the waters of Ise Bay, Owase Bay, Kumano Nada, Satsunan Shoto and the surrounding areas during 1983-1986.Most of the nitrogen scavengers were gram negative, asporogenous motile rods with polar flagella. All isolates were capable of assimilating NH4+ as a sole source of nitrogen. Pseudomonas (52.3%) was the most dominant bacterial genus. Pseudomonas and Vibrio comprised 78.5% of the nitrogen-scavenging bacteria isolated from coastal and oceanic waters of Japan.The optimum temperature, pH and NaCl concentration for the growth of the representative strains S10, S14 and S174 was near 30°C, pH 7.0-7.5, and 4.0-6.0% (w/v), respectively. Glucose was effective for the growth of nitrogen scavengers. Nitrogen-scavenging bacteria effectively utilized NH4Cl among nitrogenous compounds tested as a source of nitrogen.

Studies on marine microbial function - I. Acetylene-reducing activity of a nitrogen-fixing bacterium isolated from coastal region.

Acetylene-reducing activity of nitrogen-fixing bacterium isolated from coastal region was examined.The optimum temperature and pH for the acetylene-reducing activity of Vibrio sp. AH 30 was 27-31°C and pH5.0-7.0, respectively. Although Vibrio sp. AH 30 produced nitrogenase in the presence of oxygen, oxygen inhibited considerably acetylene-reducing activity. Low concentrations (0.1-0.2g/l) of polypepton and yeast extract enhanced acetylene reduction by Vibrio sp. AH ?? 30 cells. Sodium pyruvate, mannitol, ATP, NADP(H) and Na2S2O4 also stimulated acetylene-reducing activity of Vibrio sp. AH 30 cells.The acetylene-reducing activity of nitrogen-fixing bacteria isolated from marine environ-ments was only 1/10 of that of terrestrial N2-fixing ones.