Clinical usefulness of serum tripeptide aminopeptidase activity in diagnosing liver diseases

We examined the clinical usefulness of serum tripeptide aminopeptidase (EC 3.4.11.4) activity in diagnosing liver diseases. We found that increased tripeptide aminopeptidase activity accompanied an elevation in alanine aminotransferase activity (ALT) in the sera of patients with non-cancerous liver diseases and that these enzyme activities were correlated (r = 0.826-0.972). In contrast, an increase in tripeptide aminopeptidase activity did not coincide with an elevation in ALT activity in the sera of patients with cancerous liver diseases. We also observed a correlation in acute hepatitis and in patients following transcatheter arterial embolization of hepatoma throughout their subsequent clinical courses. The difference in serum enzyme activities for cancerous and non-cancerous liver diseases seems to result from changes in enzyme activities in cancerous liver tissues. We found that the ratio of tripeptide aminopeptidase to ALT activity in hepatoma tissues (1.9) was 4 times higher than that in normal liver tissues (0.5).