Characterization of liver-type alkaline phosphatase from human gastric carcinoma cells (KMK-2) in vitro

Alkaline phosphatase was extracted from human gastric carcinoma cells (KMK-2) under long-term culture, and its biochemical and biological properties were investigated. The enzyme was extremely heat labile and was inhibited significantly by L-homoarginine, but only slightly by L-phenylalanine, so that it was classified as a liver-type alkaline phosphatase. Comparative studies with liver and early placental alkaline phosphatases revealed that the enzymes all showed a similar extent of inhibition by amino acids, heat stability, immunological character, molecular, and other biochemical properties. However, KMK-2 alkaline phosphatase was more similar to early placental enzyme in electrophoretic and gel filtration pattern. This liver-type alkaline phosphatase was found ultrastructurally on microvilli of KMK-2 cells, but not on the lateral structurally on microvilli of KMK-2 cells, but not on the lateral surface with interdigitating folds. Prednisolone markedly decreased the content of the present isozyme. Although the present phenotype was stable during long-term culture in regard to the isozyme properties, the original cancer cells from which the cell line had been derived were L-phenylalanine sensitive and moderately L-homoarginine sensitive. This indicated that phenotypic change occurred on cultivation of cancer cells in vitro.