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Biomedical subjects

H Tokunaga

Publications and source records attributed to H Tokunaga.

At least 199 records · Page 11Linked to original sources
PubMed1977

Microassay methods for taurine and cysteine sulfinate decarboxylase activity.

Microassay methods for taurine (2-aminoethanesulfonic acid) and cysteine sulfinate decarboxylase (CSD: EC 4.1.1.29) have been developed. Cation exchange resin (Dowex 50W x 8, 200--400 mesh) was used for the separation of taurine from other fluorescamine reactive substances. The "taurine fraction" in this column chromatographic procedure was collected and fluorescence development was carried out. The maximal sensitivity obtained for taurine was 25 pmoles. The specificity, reproducibility, sensitivity and recovery for taurine obtained by this method were satisfactory enough to be used for biological applications. The activity of CSD was determined by measuring the formation of 14CO2 from DL-[1-14C]-cysteine sulfinic acid using a specially designed micro-vessel. The activity in cerebral tissues containing 5 microgram of protein was accurately detected by this microradiometrical method. Using above microassay methods for taurine and CSD activity, it was found that in the rat spinal cord, taurine is distributed rather evenly, whereas the distribution of CSD activities is uneven and the highest activity is localized at the dorsal part of the dorsal horn.

Animals↗
PubMed1977

Two omega-amino acid transaminases from Bacillus cereus.

Bacillus cereus strain K-22 produced two distinct omega-amino acid transaminases, one catalyzing the transamination between beta-alanine and pyruvic acid and the other that between gamma-aminobutyric acid and alpha-ketoglutaric aic. The two enzymes were partially purified and separated from each other by various chromatographies. beta-Alanine:pyruvic acid transaminase and gamma-aminobutyric acid:alpha-ketoglutaric acid transaminase were induced by the addition of beta-alanine and gamma-aminobutyric acid, respectively, to the growth medium. beta-Alanine transaminase showed an optimum pH of 10.0 and optimum temperature of 35 degrees C, and its Km values for beta-alanine and pyruvic acid were both 1.1 mM. gamma-Aminobutyric acid, epsilon-aminocaproic acid, 2-aminoethylphosphonic acid, and propylamine showed about 30-40% of the activity of beta-alanine as amino donors, and oxalacetic acid was as good an amino acceptor as pyruvic acid. The optimum pH and temperature of gamma-aminobutyric acid transaminase were 9.0 and 50 degrees C, respectively, and its Km value for gamma-aminobutyric acid was 2.8 mM, while that for alpha-ketoglutaric acid was 2.3 mM. gamma-Aminobutyric acid and delta-aminovaleric acid were good amino donors but other omega-amino acids were virtually inactive with gamma-aminobutyric acid transaminase; alpha-ketoglutaric acid, and to a lesser extent glyoxylic acid, were active amino acceptors. Sulfhydryl reagents specifically activated gamma-aminobutyric acid transaminase.

4-Aminobutyrate Transaminase↗