Shigeru Hoshiko

The reaction mechanisms and substrate-stereospecificities of L-alloisocitrate dehydrogenase and oxalosuccinate decarboxylase.

A sequential reaction was suggested for the conversion of L-alloisocitrate to alpha-oxoglutarate by an enzyme complex of L-alloisocitrate dehydrogenase and oxalosuccinate decarboxylase from Pseudomonas strain No. 2, during which oxalosuccinate was not released from the enzyme-substrate complex. The stereochemistry of oxalosuccinate formed by L-alloisocitrate dehydrogenase and decarboxylated by oxalosuccinate decarboxylase was opposite to that of the substrate for D-isocitrate dehydrogenase. Incubation of L-alloisocitrate with the dehydrogenase and decarboxylase in deuterium oxide provided [3-2H]-alpha-oxoglutarate, the configuration of which turned out to be the same as that produced by D-isocitrate dehydrogenase from D-isocitrate. The data suggested that enol form of alpha-oxoglutarate was involved as an intermediate in decarboxylation of oxalosuccinate by oxalosuccinate decarboxylase. L-Alloisocitrate dehydrogenase was shown to react with pro-S proton of NADH.

Isolation and Characterization of NewVirulent Actinophage φr5

A new virulent phage, φr5, was isolated from soil on Streptomyces ribosidificus SF733. Electron microscopic observation showed that this phage belongs to group B of Bradleys morphological classification. The molecular weight of φr5 DNAwas about 29×106. φr5 DNA showed resistance to many restriction enzymes. φr5 required Ca+ + for plaque formation and grew at 28°C on S. ribosidificus SF733, S. chartreusis SF1623, S. flavus, S. flavovirens, S. sulfonofaciens SF2103, S. sulfonofaciens SF21 38 and S. sulfonofaciens SF2 1 44. The restriction-modification of φr5 by the strains susceptible to this phage was examined.

Isolation and characterization of new virulent actinophage .PHI.r5.

A new virulent phage, Φr5, was isolated from soil on Streptomyces ribosidificus SF733. Electron microscopic observation showed that this phage belongs to group B of Bradley′s morphological classification. The molecular weight of Φr5 DNA was about 29 × 106. Φr5 DNA showed resistance to many restriction enzymes. Φr5 required Ca+ + for plaque formation and grew at 28°C on S. ribosidificus SF733, S. chartreusis SF1623, S.flavus, S. flavovirens, S. sulfonofaciens SF2103, S. sulfonofaciens SF2138 and S. sulfonofaciens SF2144. The restriction-modification of Φr5 by the strains susceptible to this phage was examined.