Two macromolecular complexes between alkaline phosphatase and immunoglobulin A in a patient's serum

We report the presence of two separate macromolecular complexes between an immunoglobulin and alkaline phosphatase (EC 3.1.3.1) in the serum of a patient with cholestatic liver disease. The complexes were seen as slow-moving bands on electrophoresis on polyacrylamide gel (70 g/L). Estimates of relative molecular mass for the two bands were 785 000 and 490 000 by gel chromatography on Sephacryl S300, and 640 000 and 420 000 by gradient gel-electrophoresis. Inhibitor and heat-inactivation studies showed that the two bands had similar properties, resembling the liver isoenzyme but more heat stable. Immunological studies suggested that both bands consisted of a complex of liver alkaline phosphatase with kappa type immunoglobulin A.