Isolation and kinetic properties of pyruvate kinase activated by fructose-1,6-biphosphate from Salmonella typhimurium LT-2.I.

Pyruvate kinase, activated by fructose-1,6-biphosphate from Salmonella typhimurium LT-2, has been isolated and purified to homogeneity. The enzyme, similar to that from Escherichia coli, is a tetramer with an approximate molecular weight of 240,000. The native enzyme shows optimum pH 6.8 (T = 30 degrees C). The enzymatic reaction does not require K+ ions; while Mg2+ or Mn2+ are essential for its activity. The non-activated enzyme shows sigmoid kinetics to phosphoenolpyruvate with a Hill coefficient of 2.73; the activated enzyme becomes michaelian with KSADP y KSPEP 0.25 and 0.08 mM, respectively. Both substrates excess and ATP cause enzyme inhibition. In agreement with the experimental results a steady-state random-ordered hybrid Bi-Bi mechanism with two dead-end complexes is proposed.