Abstract
In a previous publication, results on the purification, nature and mode of action of glutamic・pyruvic transaminase (GPT) from pig heart muscle were reported. In the course of the experiment, it was found that GPT was separated into two fractions on calcium phosphate gel column and starch zone electrophoresis, and they belong to the one in soluble fraction and mitochondria respectively. For solubilization of enzyme from mitochondria, several techniques, i. e., sonication (10Kc, 10min.) treatment with deoxycholate, freezing and thawing, and grinding with glass powder, gave the enzymes which have 60% of activity compared with original mitochondrial suspension. This loss is assumed to be attributed to the disruption of essential structure of mitochondria, or to the accumulation of oxalacetic acid in intact mitochondria which is measured as pyruvate. Digitonin inhibited the enzyme activity completely. GPT in soluble and in mitochondrial fractions were eluted with 0.02M phosphate buffer at pH 6.8 and 0.06M at pH 6.8 respectively on calcium phosphate gel column chromatography by stepwise and gradient eluting systems. On zone electrophoresis, they moved to cathode and separated each other. GPT preparation catalyzed the elemental reaction (C^<14>-alanine+pyruvate ⇄C^<14>-pyruvate+alanine, C^<14>-glutamate+α-ketoglutarate⇄C^<14>-α-ketoglutarate+glutamate) more strongly than original reaction (glutamate+pyruvate⇄alanine+α-ketoglutarate) with the same Km. GPT in soluble fraction has optimum pH at 9.7-9.5 and that in mitochondrial fraction at pH 8.5.
