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Biomedical subjects

T Okazaki

Publications and source records attributed to T Okazaki.

At least 469 records · Page 26Linked to original sources
PubMed1979

Purification and characterization of cytosol phosphoenolpyruvate carboxykinase from bullfrog (Rana catesbeiana) liver.

Cytosol PEP carboxykinase has been purified to electrophoretic homogeneity from bullfrog liver homogenate. The enzyme is a single polypeptide chain with a molecular weight of approximately 72,000-75,000. The purified enzyme catalyzed oxaloacetate decarboxylation (nucleoside triphosphate-supported), phosphoenolpyruvate carboxylation, and an exchange reaction between oxaloacetate and [14C]HCO3-in the presence of ITP or CTP. Manganese is absolutely required for the enzyme-catalyzed phosphoenolpyruvate carboxylation, whereas it can be replaced by Mg2+ for the oxaloacetate decarboxylation and the exchange reaction. The optimal pH of each reaction is dependent on the divalent metal ion used. The dependence of the enzyme activity on Mn2+ is markedly different in the phosphoenolpyuvate carboxylation and the oxaloacetate decarboxylation reactions.

Amino Acids↗
PubMed1978

Identification of the globin chain and the amino acid residue responsible for polymerization of bullfrog (Rana catesbeiana) hemoglobin with iodo[14C]acetamide.

The bullfrog (Rana catesbeiana) major hemoglobin dissociates into its constituent globin chains (alpha and beta) which are separated by Sulfopropyl-Sephadex C-25 column chromatography after alkylation with iodo[14C]acetamide. Each globin chain has two cysteine residues and those of the beta-globin chain in the tetramer are preferentially alkylated with iodoacetamide.

Animals↗
PubMed1978

Initiation of human parturition. X. Substrate specificity of phospholipase A2 in human fetal membranes.

The substrate specificity of phospholipase A acitivty of fetal membranes and uterine decidua was investigated with the use of synthetic substrates, and emphasis was on the specificity of fatty acid esters in the sn-2 position of glycerophospholipids. Rat liver mitochondria were also used as an enzyme source for the substrate specificity studies. Phosphatidylethanolamine was found to be hydrolyzed more rapidly than was phosphatidycholine by the phospholipase A activities of human fetal membranes and uterine decidua and of rat liver mitochondria. The phopholipase A2 in fetal membranes preferentially effected the hydrolysis of phosphatidylethanolamines containing specific fatty acids in the sn-2 position in the following order: arachidonic acid greater than oleic acid less than palmitic acid. No remarkable specificity for arachidonyl esters in the sn-2 position of phosphatidylethanolamines was observed for the phospholipase A activities of human uterine decidua or rat liver mitochondria. The results of this study are consistent with the view that human fetal membrane phospholipase A2 that preferentially hydrolyzes the phosphatidylethanolamines that contain arachidonic acid in the sn-2 position is, in part, responsible for the highly selective accumulation of free arachidonic acid in the amniotic fluid of women in labor.

Animals↗
PubMed1978

Prostaglandin E and mitogenic stimulation of human lymphocytes in serum-free medium.

Sera used in cell cultures contain significant ammounts of prostaglandins (PGs). In order to avoid any effects of contaminating PGs, the present study employed a serum-free culture medium and confirmed the inhibitory effect of prostaglandin E (PGE) on the human lymphocyte activation which had been observed previously employing a serum-containing medium. PGE1 displayed a significantly stronger inhibitory effect on the cells than previously shown. Furthermore, reported enhancement of PGE synthesis by mitogen-activated lymphocytes could not be reproduced.

Cells, Cultured↗
PubMed1978

Uracil incorporation into nascent DNA of thymine-requiring mutant of Bacillus subtilis 168.

A thymine-requiring mutant of Bacillus subtilis strain 168 accumulates short DNA chains after brief pulses with [(3)H]thymidine. Reversion of the thy mutation to thy(+) abolishes the accumulation of short DNA chains, suggesting that the accumulation is related to the thy mutation. The reason for this accumulation has been further investigated by analysis of a mutant with a defective uracil-DNA glycosidase activity (urg). The accumulation of short DNA chains in thy(-) cells is abolished by the deficiency of uracil-DNA glycosidase activity. In thy(+) cells, the deficiency of the glycosidase activity does not change the sedimentation profile of pulse-labeled DNA. DNA isolated from thy(-)urg(-) cells is fragmented by successive treatment with purified uracil-DNA glycosidase and alkali, indicating that uracil residues are present in this DNA. DNA isolated from thy(+)urg(-) cells is not fragmented by the same treatment. Significant radioactivity is detected in the dUMP region, when [(3)H]uridine-labeled DNA from thy(-)urg(-) cells is hydrolyzed and analyzed by thin-layer chromatography. Only a trace amount of radioactivity, which is not influenced by the deficiency of uracil-DNA glycosidase activity, is found in the dUMP region in DNA hydrolysates from thy(+) cells. These results suggest that, in thy(-) cells, uracil is incorporated into DNA and the accumulation of short DNA chains results from the excision-repair of this uracil whereas in thy(+) cells, uracil is seldom, if ever, incorporated into DNA.

Bacillus subtilis↗
PubMed1978

T7 gene 6 exonuclease has an RNase H activity.

T7 gene 6 exonuclease has been shown to have an RNase H activity as well as a double-strand specific DNase activity by the following experiments: The RNase H activity coelutes with the DNase activity from DEAE-cellulose, phosphocellulose, hydroxyapatite, and Sephadex G-200 columns. Gene 6 exonuclease specified by a T7 strain with a temperature sensitive mutation in gene 6 has an extremely heat-labile RNase H activity as well as a heat-labile DNase activity. T7 gene 6 exonuclease degrades the RNA region of a poly(A) . poly(dT) hybrid polymer exonucleolytically from the 5' terminus, releasing a ribonucleoside 5'-monophosphate product. When the RNA strand of a 0X174 RNA . DNA hybrid molecule synthesized with E. coli RNA polymerase is degraded, a ribonucleoside triphosphate is produced from the 5'-triphosphate terminus. Participation of T7 gene 6 exonuclease in the removal of primer RNA in discontinuous replication of T7 DNA is discussed.

Coliphages↗
PubMed1978

Plasma prostaglandin concentrations in allergic bronchial asthma.

Prostaglandin (PG) E plasma levels, measured by radioimmunoassay using anti-PGB1 antibody, were higher in asthmatic patients than in normal subjects. PGF levels measured with anti-PGF2alpha antibody, were not significantly different between normals and asthmatics. Plasma PGE/F ratios were elevated in the asthmatic patients. The results fail to support the hypothesis of decreased PGE or increased PGF production as an etiological factor in asthma.

Adolescent↗