Further studies on aminopeptidase-M in blood in children with cholestatic liver diseases and viral hepatitis.

Aim of this study was to determine and further characterize the serum aminopeptidase-M in children with liver diseases. Based on our new assay, we have shown two fractions of the enzyme. Activity of the first fraction is expressed in undiluted serum at pH adjusted from 8.5 (pH of storaged serum) to 7.4. Activity of the second fraction (cryptic activity) appears in the serum (pH 7.4) as a result of dilution and/or addition of aniline naphthalene sulfonic acid. In children with Alagille syndrome, extrahepatic biliary duct atresia, Byler's disease, and acute hepatitis due to hepatitis B virus infection, activities of both fractions are highly elevated as compared to healthy children or those with chronic viral hepatitis. Moreover, serum aminopeptidase-M seems to reflect other aspects of the pathological process than those reflected by the alanine aminotransferase and gamma-glutamyltranspeptidase. Due to increased activity and broad substrate specificity, the enzyme seems to be also a cofactor of cholestasis and hepatitis.