AMINOPEPTIDASE ACTIVITIES ON SURFACE OF MAMMALIAN-CELLS AND THEIR ALTERATIONS ASSOCIATED WITH TRANSFORMATION

Abstract

Activities of various hydrolytic enzymes were determined in rat organ homogenates and on the surface of cells from various sources, i.e., tumor cell strains, primary cultured cells, normal cells and their transformants. Alanine, leucine, methionine, phenylalanine and glycyl-proline aminopeptidases and esterase showed relatively high activities in all these organs and cells. In the kidney homogenate the aminopeptidase A activity was higher than that of aminopeptidase B. The situation was reversed in other organs; i.e., the aminopeptidase A activity was lower than that of aminopeptidase B. Normal cells derived from kidneys showed the kidney-type pattern of aminopeptidases A and B on the surface of cells, but tumor cells from various origins were of another organ type. When cultured mouse fibroblast strain C3H2K and rat fibroblast strain 3Y1 cells were transformed by SV40 or by a ts A mutant and maintained at permissive temperature, aminopeptidase A activity was drastically decreased, and the ratio of aminopeptidase A to aminopeptidase B was reduced to the levels of tumor cells. If the ts A mutant transformed cells were grown at the restrictive temperature, the ratio approached that of normal cells. In normal cells, cultivation at high or low temperature did not cause any change of the activities.