Intestinal alkaline phosphatase linked to immunoglobulin G of the kappa type.

An electrophoretically slow-moving alkaline phosphatase(orthophosphoric-monoester phosphohydrolase, EC 3.1.3.1, alkaline optimum, ALP) isoenzyme was found in the serum of a patient with osteomalacia. Molecular mass of this ALP was estimated to be 500 000 daltons. Inhibitor studies revealed that the abnormal ALP, which formed a macromolecular complex, was an intestinal isoenzyme. Immunofixation following electrophoresis demonstrated that the macromolecular ALP was a complex composed of intestinal ALP and immunoglobulin G of the kappa type. This isotype specificity of immunoglobulin suggested that the ALP immunoglobulin complex is a specific antigen-antibody complex in circulation.