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C Inagaki

Publications and source records attributed to C Inagaki.

9 recordsLinked to original sources
PubMed1978

Enzymatic decarboxylation of L-threo-3,4-dihydroxyphenylserine in rat heart.

Decarboxylation of L-threo-3,4-dihydroxyphenylserine (L-threo-DOPS) by the higher speed supernatant of the rat heart homogenate and the regional distribution of L-threo-DOPS decarboxylase activity were examined. Decarboxylation was demonstrated to occur specifically with L-isomer but not with D-isomer. Addition of pyrogallol was necessary for maximal recovery of norepinephrine. The optimal condition for decarboxylation of L-threo-DOPS by the rat heart enzyme was similar to conditions required with the enzymes from brain and kidney. Under the optimal conditions, Km and Vmax for L-threo-DOPS were 2.1 mM and 6.4 nmoles/mg protein/15 min, respectively. Decarboxylation of L-threo-DOPS was markedly inhibited by D-threo-DOPS and D-DOPA. The L-aromatic amino acid decarboxylase activity was highest in the right auricle followed by the atrial body, the left auricle, the right ventricle and the left ventricle.

Animals↗
PubMed1976

[Synthesis of norepinephrine from 3,4-dihydroxyphenylserine by L-aromatic amino acid decarboxylase of the rat brain and kidneys].

The enzymic decarboxylation of stereoisomers of DOPS was examined using rat brain and kidney decarboxylase. Optimal assay conditions for racemic threo- and racemic erythro-DOPS decarboxylation were determined by the experiments concerning 1) time course, linear for 20 min, 2) optimal pH, pH 8.2, 3) optimal temperature, 37 degrees C except racemic L-threo-DOPS decarboxylation by kidney enzyme and 4) protein concentration, 1 to 5 mg in incubation medium. Under the optimal assay condition, Km of brain enzyme for L-threo-DOPS was 1.43 X 10(-3)M and Vmax, 2.22 nmoles NE/mg/15min, and Km for racemic erythro-DOPS was 10(-3)M and Vmas, 4.3 nmoles NE/mg/15min. Km of kidney enzyme for L-threo-DOPS was 1.37 X 10(-3)M and Vmax 21 nmoles NE/mg/15min, and Km for racemic erythro-DOPS was 8.7 X 10(-4)M and Vmax, 16.7 nmoles NE/mg/15min. On the other hand, D-threo and D-erythro-DOPS were scarcely decarboxylated. Decarboxylation of L-threo-DOPS in kidney enzyme was markedly inhibited by D-threo-DOPS. Kinetic analysis revealed that the type of inhibition was non-competitive. In helically-cut strips of isolated rabbit aorta, the contractile response to NE (10(-8)g/ml) formed from L-threo-DOPS was 95% that of 1-NE (10(-8)g/ml) while the response to NE (10(-8)g/ml) formed from racemic erythro-DOPS was not detectable. These results suggest that L-threo-DOPS is a more effective precursor of natural 1-NE than racemic threo-DOPS.

Animals↗