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Vanadyl(IV) complexes with pyruvate kinase: structure-activity correlations

Thesis/Dissertation ·
OSTI ID:6935996
Pyruvate kinase is unusual among kinases in that it requires two equivalents of divalent cation as cofactors, and, in addition, has an absolute requirement for monovalent cations. Vanadyl ion (V(IV)O/sup 2 +/) was employed as a paramagnetic probe of the metal sites. Electron paramagnetic resonance spectroscopy (EPR) provided structural details concerning the interactions of the substrates and cofactors, and the structural findings have been correlated with important aspects in catalysis. Vanadyl ion is essentially inactive in the normal reaction of pyruvate kinase (P-enolpyruvate + ADP + H/sup +/ ..-->.. pyruvate + ATP), and in the enolization of pyruvate. However, significant activation is observed in the phosphorylation of the alternative substrate, glycolate, by ATP, and the vanadyl-enzyme exhibits a high HCO/sub 3/-stimulated ATPase activity compared to Mg/sup 2 +/ or Mn/sup 2 +/. EPR spectra from ternary complexes with /sup 17/O-enriched oxalate, pyruvate and glycolate show inhomogeneous broadening, indicating all three compounds to be equatorially bidentate ligands to the enzyme-bound VO/sup 2 +/. EPR experiments with /sup 17/O-labeled P-glycolate identify the phospho group as an equatorial ligand to VO/sup 2 +/.
Research Organization:
Pennsylvania Univ., Philadelphia (USA)
OSTI ID:
6935996
Country of Publication:
United States
Language:
English