Kazuyoshi Sato

Bacteriochlorophyll formation by facultative methylotrophs, Protaminobacter ruber and Pseudomonas AM 1

The unique physiological characteristic of the photosynthetic bacteria is their ability to grow anaerobically in the light, a property conferred upon them by their photosynthetic pigment systems [ 1 ] . Facultative methylotrophs, Rotaminobacter ruber [2,3] and Pseudomonas AM 1 [4] are obviously different from such photosynthetic bacteria, since they grow aerobically and do not grow anaerobically in the light. Nevertheless, they produce bacteriochlorophyll under certain conditions. As far as the author is aware, this is the first report on the formation of bacteriotihlorophyll by the microorganisms classified as non-photosynthetic bacteria. Several microorganisms such as Mycobacterium iumsassi and Neurospora crassa are known as photochromogens and can synthesize carotenoids photoinducibly [5,6] . However, there is no report on photoinduced bacteriochlorophyll formation by non-photosynthetic bacteria. This paper presents evidence for photoinduced, or photo-enhanced, bacteriochlorophyll formation by the methylotrophs, Rotaminobacter ruber and Pseudomonas AM 1.

Vitamin B12- dependent methionine synthesis in Rhizobium meliloti

Abstract Methionine, among the various additions to the medium, could only replace cobalt ion or vitamin B12 required for the growth of Rhizobium meliloti . It was demonstrated that there exists a vitamin B12-dependent terminal step in the methionine synthesis, that is, N5ue5f8CH3-tetrahydrofolate-homocysteine transmethylase, which can also catalyze the methyl transfer from CH3ue5f8B12 to homocysteine, in the cell-free extracts of Rhizobium meliloti. These facts seem to indicate that the vitamin B12-dependent pathway to methionine functions mainly among the B12-dependent enzymatic systems in the wild-type symbionts and this is the chief nutritional significance of cobalt.

A simple and sensitive method for assay of a ribonucleotide reductase system

Abstract A simple and sensitive method is described for the assay of ribonucleotide reductase. The advantage of this system is improved separation of ribonucleotides and their corresponding deoxyribonucleotides by paper chromatography using a filter paper impregnated with 0.1 m boric acid. A ribonucleotide reductase system from Rhizobium meliloti could be easily assayed by carrying out this paper chromatography of the sample obtained from the enzymic reaction with 14 C-labeled substrate.

Methylmalonyl-CoA mutase in a methanol-utilizing bacterium, Protaminobacter ruber

Many of the methanol-utilizing bacteria produce vitamin Biz [l-3], which is presumed as playing an important role in the metabolism of the cells. However, little is known on the physiological roles of vitamin Blz in these microorganisms. Recently we isolated a pink-pigmented methanolutilizing bacterium, classified as Protaminobacter ruber. It was found to synthesize a considerable amount of vitamin Biz, mainly in a form of adenosylBiz and a little in a form of methyl-Bis. Since we could demonstrate the existence of the Bi,-dependent methionine synthetase in the bacterium [4], methyl-Brs would be considered to function as the active site of this transmethylase. However, in what reaction the adenosyl-Bra formed predominantly in the cells of P. ruber participates has not been elucidated yet. Here we present an evidence that adenosylBi,-dependent methylmalonyl-CoA mutase catalyzing the following reaction exists in the cells of P. ruber.

Purification and properties of vitamin B12-dependent ribonucleotide reductase from Rhizobium meliloti.

Ribonucleotide reductase from Rhizobium meliloti grown on the cobalt-deficient medium containing methionine was purified about 37-fold by streptomycin treatment, ammonium sulfate fractionation and column chromatographies on 1st DEAE-cellulose, 2nd DEAE-cellulose and Sepharose 6B. In agar gel electrophoresis, the purified enzyme moved as a single protein band. In sedimentation velocity experiments and analytical gel filtration, the purified enzyme was proved to aggregate and disaggregate. The s20, w of the enzyme at high concentration was about 27.1. From the intercept of the extrapolated curve line, the s20, w of approximately 20 was obtained. In analytical gel filtration, the location of elution peak varied with the protein concentration placed on the column. Sodium dodecyl sulfate gel electrophoresis of the purified enzyme exhibited two bands, the molecular weights of which were estimated to be approximately 130,000 (a major band) and 110,000 (a minor band). The proportion of the major band to the minor...