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Placenta-like Alkaline Phosphatases from Human Osteosarcoma Cells¹

Orthopaedic Research Laboratories, Division of Orthopaedic Surgery [I. S., K. Y. T.], and the Department of Surgery [W. S. B.], Medical College of Ohio, Toledo, Ohio 43699

Hormone-induced alkaline phosphatases in human osteosarcoma cells (LM) were extracted and purified. Characterization of the purified enzyme showed two distinct isoenzymes. One isoenzyme was heat labile, was homoarginine inhibited, and had the electrophoretic migration of alkaline phosphatase of human osseous origin. Immunodiffusion showed that this isoenzyme reacted positively only against anti-bone alkaline phosphatase antibodies. The second isoenzyme was heat stable, was inhibited by phenylalanine, and had the same electrophoretic migration as did alkaline phosphatase extracted from mature normal human placenta. This second isoenzyme had the same antigenicity as did the normal placental enzyme. Like the D-variant placental phenotype, this second isoenzyme was inhibited by L-leucine and ehtylenediaminetetraacetic acid.

¹ Supported in part by General Research Support, Institutional Grant 2-1-4-94391, and the Ohio Chapter of the American Cancer Society.

² To whom requests for reprints should be addressed.

Received 12/21/76. Accepted 10/17/77.