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Biomedical subjects

S Murakami

Publications and source records attributed to S Murakami.

At least 901 records · Page 50Linked to original sources
PubMed1977

Partial purification and characterization of L-lactate dehydrogenase isozymes from sweet potato roots.

Lactate dehydrogenase [L-lactate: NAD oxidoreductase, EC 1.1.1.27] was isolated from sweet potato root tissues. Two species of the enzyme (isozymes I and II) were separated by DE-52 cellulose column chromatography from healthy, cut, and black-rot diseased tissues. Isozymes I and II were purified from healthy and diseased tissues, respectively. Reduction of pyruvate by NADH with either isozyme I or II was inhibited by pyruvate at high concentrations, by NAD+ and by several mononucleotides. Isozyme I was inhibited by a lower concentration of adenine nucleotide than isozyme II, and Km for pyruvate was increased markedly at acidic pH in the case of isozyme I, but only slightly in the case of isozyme II. The molecular weights of both isozymes were determined to be 150,000 and they were found to be charge isomers by polyacrylamide gel electrophoresis. The enzyme activity increased in response to infection by black-rot fungus but decreased in response to cutting.

Hydrogen-Ion Concentration↗
PubMed1976

Macromolecular synthesis after a nutritional shift-up of Bacillus subtilis.

Effects of amino acids of macromolecular synthesis in Bacillus subtilis were studied. Two mutants, CRK4001 and NIG45, that were selected as slow growers in rich media were proved to be useful to analyse early events occurring after addition of amino acids to exponentially growing cells in a glucose-salts medium (nutritional shift-up). In a wild type strain, the rate of stable RNA (sRNA: essentially ribosomal RNA) synthesis increased 2.3 fold shortly after the shift-up to the rate characteristic of the post-shift steady state growth. In contrast,sRNA synthesis in the mutant strains responded to the shift-up in two steps. Thus, shortly after the shift the rate of sRNA synthesis increased 2.2 fold as in the wild type but this increased level was maintained temporarily for 60 min and suddenly decreased to the post-shift steady state rate (1.4 fold increase). On the other hand, rates of DNA synthesis increased some 30 min after the shift directly to the post-shift steady state rates in all strains. Ratios of an origin to a terminus marker (purA/metB) began to increase exponentially to reach maximum values at 60 min after the shift, indicating that initiation of DNA replication occurred at frequencies characteristic of respective post-shift growth rates soon after the shift. These results revealed that the initial increase in the rate of sRNA synthesis and the frequency of initation of DNA replication after nutritional shift are not related to each other and are independently affected by amino acids. In concert with these findings, the increase in sRNA synthesis was not affected by inhibition of DNA synthesis for the first 60 min after the shift, while it was completely prevented by puromycin and choramphenicol. Protein synthesis for 10 min after the shift was sufficient to fully change the sRNA synthesis rate by amino acids.

Amino Acids↗
PubMed1976

Comparative studies on chemical, hemolytic and diffusion-in-gel precipitation properties of various lysosphingolipids.

Various lysosphingolipids were prepared and their chemical structures were confirmed by thin layer chromatography, infrared spectroscopy, proton magnetic resonance spectroscopy and chemical analyses of sugars, aminosugars, fatty acids and long chain bases by gas-liquid chromatography. Some hemolytic and diffusion-in-gel precipitation properties of these substances were compared with each other. Almost all of deacylated sphingolipids had approximately the same hemolytic activity. These hemolytic activities were inhibited with equal amounts of cholesterol. Aqueous solutions of digalactosylglucosylsphingosine, galactosaminyldigalactosylglucosylsphingosine and digalactosaminyldigalactosylglucosylsphingosine gave rise to non-immune precipitation lines with normal animal sera, particularly with their low density lipoproteins on agarose gel double diffusion, whereas sphingosylphosphorylcholine and neuraminylgalactosylglucosylsphingosine gave no precipitation lines at all. High concentration of lactosylsphingosine, galactosylsphingosine and glucosylsphingosine, respectively, gave rise to a slightly faint precipitation line.

Animals↗
PubMed1976

Inhibition of photophosphorylation by ATP and the role of magnesium in photophosphorylation.

ATP and pyrophosphate at high concentration (greater than 1 mM) inhibited photophosphorylation of isolated spinach chloroplasts in the normal salt medium and did not cause stimulation of electron transport. The inhibition of photophosphorylation by ATP or pyrophosphate was shown to be abolished by the addition of excess MgCl2, ADP and phosphate. It has been demonstrated that the rates of photophosphorylation in the absence and presence of ATP or pyrophosphate are determined similarly by the concentrations of magnesium-ADP (Mg - ADP-) and magnesiumphosphate (Mg - Pi) complexes. It is highly probable that Mg - ADP- and Mg - Pi, but not free ADP and free phosphate, are the active form of the substrates of photophosphorylation. This is in support of the view that ATP inhibits photophosphorylation by decreasing the concentration of Mg2+ which is available for the formation of the complex with ADP and phosphate.

Adenosine Diphosphate↗