Branched Chain Amino Acid Transaminases in Rat Ascites Hepatoma Cells

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A new branched chain amino acids (valine, leucine and isoleucine)-α-ketoglutaratetransaminase was isolated and characterized from rat ascites hepatoma cells (AH 130). The supernatant of the tumor homogenate was applied on DEAE cellulose column chromatography and two active fractions were eluted. The first fraction was eluted by 0.02 M phosphate buffer, and the enzymological properties (substrate specificity, Km values for the substrates, activation by 2-mercaptoethanol, pH optimum, and inhibition of the activity by anti-serum against hog heart transaminase) revealed that this enzyme (Enzyme I) is a similar type to that found in various normal rat tissues. It was found, however, that there is another active fraction which is eluted by 0.2 M buffer. This fraction was further purified by CM cellulose and Starch electrophoresis. The active enzyme (Enzyme III) thus obtained was shown by ultracentrifugation to be a single protein. The enzyme properties were very similar to those of Enzyme I as described above, although Km values were two times higher and activation by 2-mercaptoethanol was half of those of the Enzyme I. The most remarkable difference is that anti-serum against hog heart enzyme did not inhibit the Enzyme X. The mitochondria of this tumor cells contained only the Enzyme I. Yoshida sarcoma cells also have both of the enzymes (I and X). Normal rat liver contained two enzymes, among which one is the Enzyme I, whereas another one is eluted by 0.18 M buffer but distinctively earlier fraction than the Enzyme AI and the substrate specificity was limited to leucine. It was not activated by 2-mercaptoethanol. Comparison and possible relation between these enzymes were discussed.
Japan Society of Clinical Chemistryの論文

Branched Chain Amino Acid Transaminases in Rat Ascites Hepatoma Cells

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