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Biomedical subjects

S Shirai

Publications and source records attributed to S Shirai.

At least 127 records · Page 7Linked to original sources
PubMed1980

Methylamine dehydrogenases of Methylomonas J and Pseudomonas AM1. Hybridization of light and heavy subunits and some properties of an isolated hybrid enzyme.

Hybridization reactions were carried out in vitro between the light and heavy subunits of two methylamine dehydrogenases obtained from Methylomonas J (formerly Pseudomonas sp. J) and Pseudomonas AM1. Enzymatic activity was restored with a combination of L3(MW: 13,000) and HA(MW: 40,000) but not with LA(MW: 13,000) and HJ(NW: 40,000). This active hybrid enzyme was isolated with a Sephadex G-150 column after incubation of LJ and HA. Its molecular weight was nearly identical to that of the two native enzymes (MW: 105,000). The electrophoretic pattern of proteins cross-linked by dimethyl suberimidate showed the formation of a tetrameric structure. Its absorption spectrum was similar to that of the native enzymes. The specific activity was 4.3 and the substrate specificity resembled that of the Methylomonas J enzyme rather than that of the Pseudomonas AM1 enzyme. Michaelis constants were 290 microM for methylamine and 14 microM for phenazine methosulfate. The circular dichroism spectrum and thermal stability resembled those of the Pseudomonas AM1 enzyme. No appreciable amount of an inactive hybrid enzyme was formed in the reaction between LA and HJ, there being neither restoration of the enzymatic activity nor formation of cross-linked tetrameric proteins with dimethyl suberimidate. Hybridization of LJ and HA was further confirmed by the appearance of three enzymatic active bands on a gel after electrophoresis of an incubation mixture of LJ, HJ, and HA. The results are consistent with a previous observation; the two methylamine dehydrogenases from either obligate of facultative metaylotrophs are the alpha 2 beta 2-type and homologous enzymes. It is also suggested that substrate specificity and catalytic activity are directed by the light subunit, and binding affinity of the substrate to the active site, electrophoretic mobility, and thermal stability of the enzyme are endowed by the heavy subunit.

Kinetics↗
PubMed1978

Methylamine dehydrogenase of Pseudomonas AM1. A subunit enzyme.

A methylamine dehydrogenase was purified to homogeneity from Pseudomonas AM1 and obtained in crystalline form. It was found to be a subunit enzyme composed of two kinds of subunit, light and heavy. These two subunits were isolated by Sephadex G-100 gel chromatography after incubation of the enzyme with guanidine hydrochloride. Molecular weights of 13,000 daltons for the light subunit and 40,000 daltons for the heavy subunit were estimated by SDS-polyacrylamide gel electrophoresis, and the molecular weight of the native enzyme was found to be 105,000 daltons by Sephadex G-200 gel chromatography. The enzyme and its subunits were also analyzed for amino acid composition, isoelectric point, and absorption fluorescence, and CD spectra, as well as for the effects of pH, thermal treatment, and guanidine hydrochloride treatment. Both the subunits were absolutely required for enzymatic activity, either subunit alone being inactive. It could be deduced from the absorption and fluorescence spectra of the subunits that the prosthetic group of the enzyme was bound solely to the light subunit. These results suggest that the enzyme is a subunit enzyme similar to that of Pseudomonas sp. J, of the alpha2beta2 type.

Amino Acids↗
PubMed1977

Traumatic middle meningeal arteriovenous fistula. Report of 3 cases and analysis of 32 cases.

Three cases of traumatic middle meningeal arteriovenous fistula are reported and 32 cases, including ours, reported in the literature are analyzed. In these 32 cases, the appearance of the arteriovenous fistula at angiography exhibited one of three different configurations: type 1, the middle meningeal vein shows a railway configuration; type 2, the middle meningeal vein shows a rod configuration; type 3, extravasation of contrast material and/or pseudoaneurysm are concomitant. In correlating the angiographic type and clinical course, the following tendencies were observed: the clinical course was good in type 1, fair in type 2 and poor in type 3, respectively.

Adult↗