Pyruvate carboxylase and phosphoenopyruvate carboxykinase in cultured human fibroblasts.

The activities of pyruvate carboxylase and phosphoenolpyruvate carboxykinase were measured in cultural human fibroblasts. Considerable variation was observed in strains derived from different individuals. The activities of both enzymes throughout the culture cycle were measured in two strains. In these strains the specific activities of the enzymes increased during log phase and remained constant during the stationary phase. However, one cell strain exhibited a high activity of pyruvate carboxylase which remained unchanged throughout the culture cycle, suggesting that this enzyme may be regulated differently in different strains of cultured human cells. Familial studies suggest that the observed variations in pyruvate carboxylase activity may be due to a genetic polymorphism.