Purification of gamma-glutamyltransferases from rat hepatomas and hyperplastic hepatic nodules, and comparison with the enzyme from rat kidney.

Abstract

y-Glutamyltransferases that increase during rat hepatocarcinogenesis were compared Âimmunochemically and electrophoretically with the enzyme from the adult rat kidney. The activity of this enzyme did not differ among hyperplastic hepatic nodules and histologically different primary hepatomas induced by A/-2-fluorenylacetamide, dimethylnitrosamine and 3'-methyl4-dimethylaminoazobenzene; thus this enzyme was confirmed to be a useful marker for preneoplastic hepatocytes. The enzymes purified from the Yoshida ascites hepatomas and primary hepatomas as well as from hyperplastic nodules were immunologically identical with the kidney enzyme in the activity inhibition and in the double diffusion tests using antibodies against the enzymes from the Yoshida AH 13 and from the kidney. They also consisted of heavy and light subunits, almost identical with those of the kidney enzyme on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, as well as immu nologically. However, on isoelectric focusing in polyacrylamide gel the purified kidney enzyme showed multiple molecular forms, while the enzymes purified from hyperplastic nodules and hepatomas showed a single form, which was more acidic than any form of the kidney enzyme, apparently owing to a higher content of sialic acid. These results indicate that yglutamyltransferases that increase in hepatocarcinogenesis are identical with the kidney enzyme in the protein portion, but differ in the sugar portion. This appears to be an oncofetal alteration of this enzyme.