Isoenzyme Composition of Human Plasma Monoamine Oxidase in Normal Subjects and in Fibrotic Liver Disease 1

Abstract

Summary

Hydroxyapatite column chromatography elution profile reveals characteristic differences between monoamine oxidase (MAO) isolated from normal human plasma and from patients with hemochromatosis having hepatic fibrosis. In normal plasma, the α form constitutes about 84% of the enzyme, with the remainder in the β and γ forms. By contrast, in hemochromatosis there is less α form (less than 40%), an additional α₁ form (about 20%) which was eluted immediately after α form, increased β form (more than 25%), and no significant difference in γ form. When calculated on the basis of total amount per liter, hemochromatosis is characterized by elevation of β form (3- to 10-fold) and the presence of α_1. These results also appear to indicate that the mulitple forms separated by hydroxyapatite column chromatography represent true multiplicity of human plasma MAO in vivo.

The authors would like to thank Drs. John P. Kirchner, Lewis E. Wright, and Francis Garcia-Torres for providing patients blood samples and to Linda S. Yeck and Aleksandras Radzius, Jr., for their editorial and illustrative assistance.