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Biomedical subjects

A Funatsuka

Publications and source records attributed to A Funatsuka.

4 recordsLinked to original sources
PubMed1984

The utilization of carnosine in rats fed on a histidine-free diet and its effect on the levels of tissue histidine and carnosine.

Carnosine can support the growth of rats fed on a histidine-free diet. Rats fed on the histidine-free diet lost weight rapidly for a few days, then remained at a relatively constant weight for 2 weeks at least. However, rats fed on a 0.90% carnosine diet, which contains histidine equimolar to that in a 20% casein diet, increased their weight at the same rate as rats fed on a 20% amino acid diet simulated with casein. On the other hand, the growth of rats fed on a 5% carnosine diet was about 70% compared with that of control rats fed on the 20% amino acid diet for a 2-week experimental period. Carnosinase activity was not significantly affected in the kidney of rats fed on the histidine-free or the 5% carnosine diet. On the other hand, carnosinase activity in the small intestine of rats fed on the histidine-free diet was significantly increased. Histidine content of serum of rats fed on the histidine-free diet decreased to 1/3 of that of control rats, while that of rats fed on the 5% carnosine diet increased to about 14 times. Carnosine content of rat gastrocnemius muscle increased with carnosine content of diets, followed by an increase of histidine in the muscle. However, carnosinase activity of gastrocnemius muscle was not affected by carnosine in diets.

Animals↗
PubMed1983

Inhibitory effect of 6-azauracil on purified rabbit liver 4-aminobutyrate aminotransferase.

Among uracil derivatives investigated, 6-azauracil, 6-azathymine, and 5-iodouracil were found to be potent inhibitors of purified rabbit liver 4-aminobutyrate aminotransferase while 6-azauridine and 6-azauridine 5'-phosphate were not. The enzyme inhibited by 6-azauracil was reactivated by dialysis but not by addition of pyridoxal 5'-phosphate. 6-Azauracil acted as a non-competitive inhibitor with respect to beta-alanine as well as 2-oxoglutaric acid, and had a K1 of approximately 0.7 mM at pH 7.3. The kinetic data suggested that 2-oxoglutaric acid acted as an inhibitor as well as an amino acceptor for the enzyme; a catalytic site was associated with an apparent Km of 0.15 mM for 2-oxoglutaric acid and a low affinity site was associated with an I50 of approximately 5 mM for the 2-oxo acid. With inhibitory concentrations of 2-oxoglutaric acid as substrate the inhibitory effect of 6-azauracil was considerably diminished. From these findings, the inhibitory effect of 6-azauracil was revealed to be different from that of structural analogs of 4-aminobutyric acid showing that 6-azauracil is a new type of 4-aminobutyrate aminotransferase inhibitor.

4-Aminobutyrate Transaminase↗
PubMed1983

Zinc as activating cation for muscle glycolysis.

Zinc cation performed a role of activator as well as inhibitor for production of lactate from glucose 6-phosphate in the cytosol fraction of rat muscle. The pH optimum for glycolysis was 7.3 when Zn2+ acted as an activator. At concentrations lower than 0.46 mM, Zn2+ was shown to be a more effective activator than Mg2+ with an apparent K 1/2 of approximately 0.1 mM. However, at concentrations higher than 0.5 mM, Zn2+ inhibited lactate production. The activatory as well as inhibitory effect of Zn2+ on lactate production was investigated by the estimation of glycolytic intermediates. From the crossover plot, lactate production reflected phosphofructokinase activity, when Zn2+ was used as a catalytic cation for both reactions. Phosphofructokinase activity in purified muscle was activated by Zn2+ with an apparent Km of approximately 0.05 mM, but at high Zn2+ concentrations, the enzyme activity was inhibited with an I50 of 0.23 mM in the presence of ATP. From these findings, it appears that lactate production might also depend on phosphofructokinase activity when Zn2+ is used as an activating cation.

Animals↗