Serum alkaline phosphatase isoenzymes linked to immunoglobulin G.

An unusual isoenzyme pattern of serum alkaline phosphatase was found in a patient with skeletal abnormalities due to multiple epiphyseal dysplasia and it was demonstrated that the abnormal pattern was caused by complex formation between serum alkaline phosphatase and immunoglobulin G of the lambda class. Physicochemical studies of the patient's serum alkaline phosphatase showed the properties of an osseous enzyme. Evidence was obtained indicating that the complexing occurred in vitro and that the patient's immunoglobulin G had the ability to bind the hepatic and osseous isoenzymes selectively but not to bile, placental and intestinal isoenzymes. No abnormality was detected in the leucocyte isoenzyme pattern. The relationship between the occurrence of complex formation and the patient's bone disease was not established.