Jun 29, 1976

Dual divalent cation requirement for activation of pyruvate kinase; essential roles of both enzyme- and nucleotide-bound metal ions

Biochemistry
R K Gupta, R M Oesterling

Abstract

Rabbit muscle pyruvate kinase requires two divalent cations per active site for catalysis of the enolization of pyruvate in the presence of adenosine 5'-triphosphate (ATP). One divalent cation is bound directly to the enzyme and forms a second sphere complex with the bound ATP (site 1). The second divalent cation is directly coordinated to the phosphoryl groups of ATP and does not interact with the enzyme (site 2). The essential role of the divalent cation at site 1 is shown by the requirement for Mg2+ or Mn2+ for the enolization of pyruvate in the presence of the substitution inert Cr3+-ATP complex. The rate of detritiation of pyruvate shows a hyperbolic dependence of Mn2+ concentration in the presence of high concentrations of enzyme and Cr3+-ATP. A dissociation constant for Mn2+ from the pyruvate kinase-Mn2+-ATP-Cr3+-pyruvate complex of 1.3 +/- 0.5 muM is determined by the kinetics of detritiation of pyruvate and by parallel Mn2+ binding studies using electron paramagnetic resonance. The essential role of the divalent cation at site 2 is shown by the sigmoidal dependence of the rate of detritiation of pyruvate on Mn2+ concentration in the presence of high concentrations of enzyme and ATP yielding a dissociation constant of 2...Continue Reading

Mentioned in this Paper

Manganese
Cations, Divalent
Chromium
Pyruvate Measurement
Pyruvate Kinase
Plasma Protein Binding Capacity
Pyruvate
Chinchilla Rabbits
Protein Conformation
Pyruvate Kinase Measurement

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