Release of glycolytic enzymes from cultivated tumor cells

Several types of cultured cells release glycolytic enzymes into their suspending medium. This effect is most obvious with tumor cells, especially with their ascites forms. Erythrocytes do not release glycolytic enzymes. The total extracellular phosphoglucose isomerase activity consists of two components. One part is dissolved in the medium, the other one is sedimentable at 150 X g together with the cells. The latter seems to be localized at the cell surface. At densities of about 10(6) cells/ml maximum activity in the medium is reached within 5--10 min. After that no further release of enzyme activity can be observed. Serum reduces the rate of enzyme release considerably. This effect can be reversed by washing with protein free media. Treatment with trypsin leads to high extracellular phosphoglucose isomerase activities of the cells which originally show low external enzyme activity. Erythrocytes do not show any effect with trypsin, ascites tumor cells do not alter their high extracellular enzyme activity. At a density of 10(5) cells/ml, Yoshida acites tumor cells, cultured in vitro, release about 12% of originally intracellular phosphoglucose isomerase activity by 5 elutions with fresh medium. The process of enzyme release shows a certain selectivity in respect to different glycolytic enzymes. Aldolase exhibits the highest activity in the medium in relation to its homogenate activity.