Further Studies on Aminopeptidase-M in Blood in Children with Cholestatic Liver Diseases and Viral Hepatitis

Aim of this study was to determine and furthercharacterize the serum aminopeptidase-M in children withliver diseases. Based on our new assay, we have showntwo fractions of the enzyme. Activity of the first fraction is expressed in undiluted serumat 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 sulfonicacid. In children with Alagille syndrome, extrahepaticbiliary duct atresia, Byler's disease, and acutehepatitis due to hepatitis B virus infection, activities of both fractions are highly elevated ascompared to healthy children or those with chronic viralhepatitis. Moreover, serum aminopeptidase-M seems toreflect other aspects of the pathological process than those reflected by the alanine aminotransferaseand gamma-glutamyltranspeptidase. Due to increasedactivity and broad substrate specificity, the enzymeseems to be also a cofactor of cholestasis andhepatitis.