OCCURRENCE OF THE CRABTREE EFFECT IN HELA-CELLS

The occurrence of a Crabtree effect in HeLa cells was detected. Some p roperties of pyruvate kinase (PK) were also evaluated. Hexose phosphat e, triose-phosphate and phosphoenolpyruvate (PEP) significantly decrea sed the oxygen consumption of digitonin-permeabilized HeLa cells, whic h were oxidizing succinate. The Crabtree effect promoted by PEP was co ncentration-dependent and was lowered by an increase of ADP concentrat ion, suggesting a participation of PK. The dependence of fructose-1,6- bisphosphate (FDP) by HeLa cell PK was observed. The PK of HeLa cells was inhibited by L-alanine only in the absence of FDP, while in the pr esence of the metabolite, an increase in the activity was observed. PK was also inhibited in the presence of L-histidine and L-leucine, whil e L-serine promoted activation. L-Cysteine and L-phenylalanine also in hibited the PK of HeLa cells. This, together with the sigmoidal charac ter in relation to substrate concentration, suggests the presence of t he K-type of PK in HeLa cells. (C) 1998 John Wiley & Sons, Ltd.