The direct synthesis of phospho <i>enol</i> pyruvate from pyruvate by <i>Escherichia coli</i>

Abstract

Abstract Extracts of Escherichia coli are shown to contain an enzyme system which in the presence of Mg2+ catalyses the direct formation of phosphoenolpyruvate from pyruvate and ATP with concomitant formation of AMP and inorganic phosphate. This enzyme, which has been designated 'phosphoenolpyruvate synthase' (PEP-synthase) has been purified 80-fold and is free of pyruvate kinase activity; PEP synthesis proceeded most rapidly at pH 8 to 8.5. At pH values between 6.2 and 7.5 the enzyme can catalyse the formation of ATP and pyruvate from PEP, AMP and inorganic phosphate; if arsenate is used instead of phosphate, pyruvate andADP are produced instead. Studies of the enzymic formation ofPEP with ATP specifically labelled with 32P, and of the reverse reaction with [U-14C]AMP, suggest that the PEP-synthase reaction involves the transfer of a pyrophosphoryl-group. The physiological role of PEP-synthase has been demonstrated with mutants of E. coli devoid of the enzyme: in contrast to wild-type organisms, such mutants neither grow on pyruvate, lactate or alanine, nor form glycogen from lactate. It is thus concluded that PEP-synthase plays an important role in the anaplerotic and the biosynthetic reactions which enable the organisms to grow on pyruvate as sole carbon source.