Human Alkaline Phosphatase

Abstract

The antigenic distinctiveness of individual organ-specific isoenzymes of human alkaline phosphatase was shown by immunochemical means. A two-step method involving two separate antigen-antibody reactions was utilized to identify and measure the isoenzymes. The first reaction consisted of reaction of the isoenzyme with its antiserum; the second reaction consisted of precipitating the enzyme-antibody complex with anti-γ-globulin. The second reaction was necessary because the enzyme was neither inhibited nor precipitated by specific antibody. By this method, individual isoenzymes could be identified from mixtures of isoenzymes. The results clearly show that antibody to liver phosphatase and antibody to placental phosphatase were specific for their respective homologous antigens, and did not react with alkaline phosphatase from bone, neutrophils, kidney, or intestine. Thus, there are at least three antigenic types of alkaline phosphatases: one derived from liver, one from placenta, and one or more from other organs.