Peroxisome localized human hepatic alanine-glyoxylate aminotransferase and its application to clinical diagnosis

The subcellular localization of alanine-glyoxylate aminotransferase (EC 2.6.1.44 l-Alanine:glyoxylate aminotransferase) of adult human liver was examined by sucrose density gradient centrifugation. The enzyme sedimented at the same density as catalase, indicating that it was localized in the peroxisomes. Alanineglyoxylate aminotransferase activity in the liver of patients with cirrhosis was about 65% of that of normal liver or 71% of that from patients with chronic hepatitis, but its activity in the serum of patients with cirrhosis was higher than that from patients with chronic hepatitis. Patterns of activity of alanine-glyoxylate aminotransferase in liver and serum differed from those of aspartate-2-oxoglutarate aminotransferase and ornithine carbamoyltransferase that have a different intracellular location. Serum immunoreactive alanineglyoxylate aminotransferase (Im-AGT) was measured by enzyme-linked immunoadsorbent assay (ELISA). The Im-AGT levels (mean ± SEM) in acute (80 ± 13 μg/L) and chronic (72 ± 4 μg/L) hepatitis were higher than those of normal controls (44 ± 1 μg/L). However, the difference between acute and chronic hepatitis was not statistically significant. The level in liver cirrhosis (54 ± 3 μg/L) was lower than those of the hepatitides but higher than that of normal controls. The apparent half-life of serum Im-AGT of patients who underwent liver lobectomy by a microwave tissue coagulation method was approximately 3–4 days.