Determinants of glycolytic rate in normal and transformed chick embryo fibroblasts.

We have investigated the increased rate of glycolysis following transformation of chick embryo fibroblasts by Rous sarcoma virus. In both normal and transformed cells the regeneration of adenosine 5 -diphosphate and orthophosphate was found to be the rate-limiting factor for glycolysis. The plasma membrane Na -K -adenosine5 -triphosphatase (ATPase) was a major contributor to adenosine 5 -diphosphate and orthophosphate regenera tion in the fibroblasts, but its contribution was not changed by viral transformation. Neither protein synthe sis, nor nucleic acid synthesis, nor microtubular function contributed significantly to the adenosine 5 -diphosphate and orthophosphate pools required for glycolysis either before or after transformation. Measurements of oxidative phospnorylation and of ATPase activity of isolated mito chondria did not reveal any changes following transfor mation that could account for the increased rate of glycol ysis. We propose that an ATPase, which is not sensitive to conventional inhibitors of the Na -K -ATPase or mito chondria! ATPase, appears or is increased after transfor mation. Culturing chick embryo fibroblasts in the presence of artificial ATPase activators, such as dinitrophenol or gramicidin, mimicked some of the characteristic changes induced by viral transformation. The apparent Km of gly colysis for glucose was decreased by about 10-fold, and the apparent Vmaxof hexose transport was increased by about 4-fold. In contrast to transformation, ATPase acti vators did not change the apparent Vmaxof glycolysis or the activity of hexokinase, nor did they mimic the morpho logical and growth characteristics of transformed cells.