Detection of Leucine Aminopeptipase Isozyme by Agar-Gel Electrophoresis; with Reference to Various Diseases and Pregnancy

A method for detecting leucine aminopeptidase (LAP) isozyme in human serum using agar gel electrophoresis was developed. This method excels other methods heretofore in use in simplicity and efficiency. By this method LAP isozyme can be detected in normal human serum in the α_1-globulin fraction or in the position intermediate between albumin and α_1-globulin of serum protein. LAP activity bands can be detected in positions corresponding to albumin and postalbumin of serum protein with liver homogenate, in positions corresponding to α_2-globulin and β-globulin fractions with pancreatic homogenate, in a position corresponding to α_1 globulin fraction with duodenal and renal homogenates, and positions corresponding to α_1-globulin and α_2 globulin fractions with bile homogenate. The serum leucine aminopepidase zymograms of 200 cases of various diseases, including 123 cases of hepatobiliary diseases, and 48 pregnant women were observed. LAP zymograms of normal human serum are of two types, namely Aα_1 type and α_1 type, but in hepatobiliary diseases 1 or 2 other LAP activity bands appear so that zymograms are different, I.e., Aα_1+α_1 type or Aα_1+α_2+α_2+β type. LAP zymograns were mainly Aα_1 type in such conditions as hepatitis and liver cancer which are for the most part distubances of the liver parenchyma, but almost all hepatobiliary obstruction diseases due to cholelithiasis or cancer presented the Aα_1+α_2 and Aα_1+α_2+α_2+β types. The Aα_1+α_2+α_2+β type is peculiar to bile duct obstruction. The serum of women in the latter half of pregnancy (after the sixth month) showed just one activity band (α_2 type) in a position corresponding to the position of α_2 globulin in the serum.