Complexes of serum gamma-glutamyltransferase with apolipoproteins and immunoglobulin A

We have detected complexes between gamma-glutamyltransferase and apolipoproteins or immunoglobulin A in sera from patients with hepatobiliary diseases but not in sera from healthy individuals. An average of 52.4% of the enzymic activity was precipitated by antiserum against apolipoprotein A, 29.9% by antiserum against apolipoprotein B, and 9.7% by antiserum against immunoglobulin A. Fifty to 60% of the enzyme activity was inhibited in the immunoprecipitates from the transferase fraction bound to apolipoprotein A or immunoglobulin A, and 21% in the fraction bound to apolipoprotein B. We identified the complexed transferase fractions by electrophoresis.