Key Role of Phosphoenolpyruvate in the Regulation of Glycolysis-Gluconeogenesis in Thermus thermophilus HB 8

Abstract

The in vivo concentrations of metabolites and the level of enzymes were measured to elucidate the regulatory mechanism by phosphoenolpyruvate of glycolysis-gluconeogenesis in an extreme thermophile, Thermus thermophilus HB8. Glucose 1-phosphate, glucose 6-phosphate, fructose 6-phosphate, and fructose 1,6-bisphosphate were low, and phosphoenolpyruvate was high in the cells growing on polypeptone-yeast extract (PY cells). On the contrary, phosphoenolpyruvate was low and hexose phosphates were high in the cells growing on glucose-polypeptone-yeast extract (GPY cells). The difference in the values of adenylate energy charge was not observed between PY and GPY cells. Among various enzymes, phosphofructokinase and fructose 1,6-bisphosphatase level changed markedly; the former was high in GPY cells and the latter in PY cells. It is reasonably considered that PY cells may turn on gluconeogenesis and GPY cells on glycolysis. The in vivo regulatory functions of key enzymes, phosphofructokinase, fructose 1,6-bisphosphatase, and pyruvate kinase, and the important roles of phosphoenolpyruvate and fructose 6-phosphate were discussed from these findings.