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Biomedical subjects

S Hongo

Publications and source records attributed to S Hongo.

64 records · Page 4Linked to original sources
PubMed1984

Inhibition of rat liver asparagine synthetase by Cibacron Blue F3GA.

Cibacron Blue F3GA, a blue chromophore of Blue Dextran, inhibited the activity of rat liver asparagine synthetase uncompetitively with respect to glutamine (Kii = 7.8 mumol/l), competitively with respect to aspartate (Kis = 3.1 mumol/l) and noncompetitively with respect to ATP (Kii and Kis = 5.0 mumol/l). The inhibitions were linear against the dye concentrations. These results are compatible with the postulate that asparagine synthetase reaction proceeds through a ping pong mechanism in which glutamine is bound first, followed by glutamate release, and then aspartate and ATP is bound in order. The experiments demonstrate that the dye could be useful in analyzing the kinetic mechanism of asparagine synthetase.

Adenosine Triphosphate↗
PubMed1983

Some molecular properties of asparagine synthetase from rat liver.

Asparagine synthetase purified from rat liver reveals two species (slower migrating band I and faster migrating band II) when subjected to polyacrylamide gel electrophoresis under nondenaturing conditions (S. Hongo and T. Sato (1981) Anal. Biochem. 114, 163-166). We have investigated some molecular properties of these species. Elution of band I from the gel and re-electrophoresis showed that band I yielded band II similar to that of the initial run. Peptide maps by limited proteolysis were very similar and amino acid compositions were also alike in the two species. L-Lysine was identified as the sole NH2-terminal amino acid in both the species. By cross-linking experiments the enzyme was shown to be a dimeric protein. When the purified enzyme was subjected to isoelectric focusing the enzyme activity and protein focused at pH 6.0 in a single peak. These results demonstrate that rat liver asparagine synthetase is composed of two identical subunits. The enzyme, inactivated by storage at -20 degrees C for about 3 months, showed aggregated forms in polyacrylamide gel electrophoresis, and was reactivated markedly by the addition of dithiothreitol.

Animals↗
PubMed1979

Effect of dietary protein content on the activity of rat liver asparagine synthetase.

The activity of rat liver asparagine synthetase [EC 6.3.1.1]increased when animals maintained on 25% protein diet were placed on 15% or 6% protein diet. The enzyme activity level rose within one day, reached a maximum in 7 or 10 days after switching the diet and thereafter dropped gradually. During the purification of the enzyme from rats on 25% or 6% protein diet, the yield and increase of the specific activity were similar in the two groups. Combination of the liver extracts from two such groups demonstrated that the amount of endogeneous inhibitors of the enzyme did not change on replacing the diet. The elevation of the enzyme activity in rats fed 6% casein diet was suppressed by an injection of cycloheximide or actinomycin D. It is suggested that the change in the enzyme activity was due to alteration of the amount of the enzyme.

Animals↗
PubMed1978

Purification and properties of asparagine synthetase from rat liver.

Asparagine synthetase (L-aspartate:ammonia ligase (AMP-forming, EC 6.3.1.1) activity in rat liver increased when the animals were put on a low casein diet. The enzyme was purified about 280-fold from the supernatant of rat liver homogenate by a procedure comprising ammonium sulfate fractionation. DEAE-Sepharose column chromatography, and Sephadex G-100 gel filtration. The optimal pH of the enzyme was in the range 7.4-7.6 with glutamine as an amide donor. The molecular weight was estimated to be approximately 110,000 by gel filtration. Chloride ion was required for the enzyme activity. The apparent Km values for L-aspartate, L-glutamine, ammonium chloride, ATP, and Cl- were calculated to be 0.76, 4.3, 10, 0.14, and 1.7 mM, respectively. The activity was inhibited by L-asparagine, nucleoside triphosphates except ATP, and sulfhydryl reagents. It has been observed that the properties of asparagine synthetase from rat liver are not so different from those of tumors such as Novikoff hepatoma and RADA 1.

Amino Acids↗
PubMedDate not supplied

Mechanism for splenocyte-mitogenesis induced in mice by water-extract of coniferous slash pine.

A water extract of wood chips of coniferous slash pine induced appreciable splenocyte-mitogenesis in healthy adult, aged, and also tumour-bearing mice. Mitogenesis was induced mainly in B-cell subset of splenocytes. The induction was not mediated by IL-2 or IFN gamma released from the activated helper T-cell. It may be worth noting that this extract could be included in a new type of immunomodulator for promotion of the host defense mechanism.

Animals↗
PubMedDate not supplied

Expression of asparagine synthetase mRNA through asparagine independent signal transduction pathway that might involve protein kinase C in BALB3T3 cells.

Basal level of asparagine synthetase mRNA in BALB3T3 cells was elevated when the cells were shifted from medium containing a high concentration (3.3 mM) of asparagine to one lacking asparagine. We then studied whether the expression of asparagine synthetase mRNA is also mediated through other asparagine-independent signaling pathways. BALB3T3 cells grown to near confluence were quiesced by serum-starvation, and various agents were then added to the culture to examine the enzyme activity and mRNA level of asparagine synthetase. 12-O-tetradecanoylphorbol-13-acetate (TPA), a direct activator of protein kinase C (PKC), elevated dose and time dependently the level of asparagine synthetase mRNA even in Eagle's minimum essential medium with alpha modification (MEM alpha) that contains protein-constituting 20 amino acids and is supplemented with 3.3 mM asparagine. Staurosporine and H-7, PKC inhibitors, strongly blocked the fetal bovine serum-dependent accumulation of asparagine synthetase mRNA. TPA could also enhance the activity of asparagine synthetase within 24 h at concentrations of more than 10 nM. These results suggest that expression of asparagine synthetase gene can be induced both through a pathway that involves PKC and through a pathway the origin of which is a reduced concentration of asparagine in BALB3T3 cells.

3T3 Cells↗