Glycylproline dipeptidyl aminopeptidase and gamma-glutamyl transpeptidase in human hepatic cancer and embryonal tissues.

Changes of glycylproline dipeptidyl aminopeptidase (GPDA) and gamma-glutamyl transpeptidase (gamma-GTP) activities and their subcellular distributions were compared in human hepatic cancer and embryonal tissues. The activity of GPDA in cancer tissues was significantly higher than that found in healthy liver, though there were no significant differences between fetal and adult livers. The placenta, however, had the highest GPDA activity. The activity of gamma-GTP, on the other hand, was increased significantly not only in cancer tissues but also in live tissues adjacent to the tumor, and it was higher in the fetal liver but much lower in the placenta. Subcellular distribution of GPDA was also different from that of gamma-GTP in cancer tissues, especially after postmortem changes. These results suggest the possibility that GPDA has carcinoembryonic characters similar to gamma-GTP, but the mechanisms, whereby serum activities of these two enzymes were increased in hepatocellular carcinoma patients, are different from each other.