Further investigation of a variant of the placental alkaline phosphatase in human hepatic carcinoma.

Evidence is presented for the occurrence of an apparently identical alkaline phosphatase isozyme in sera and cancer tissues of different patients with hepatocellular carcinoma. The enzyme resembles the D-variant phenotype of the placental alkaline phosphatase in inhibition of amino acids including L-phenylalanine and L-leucine, ethylenediaminetetraacetate, and urea, and also in the molecular weight. However, it differs from it in heat stability, electrophoretic mobility, pH optimum and inhibition by phosphate. Immunochemically, the hepatoma-associated enzyme possesses antigenicity partially common to the placental isozyme. These facts, in addition to its almost exclusive localization in hepatoma tissue, suggest that the enzyme is produced by the hepatoma.