title: Wheat germ phosphoglycerate mutase: evidence for a metalloenzyme.
abstract: Wheat germ phosphoglycerate mutase, exposed to 3.4 M guanidinium chloride at 22 degrees C and pH 7.8, slowly undergoes time-dependent inactivation which can be fully reversed by adding excess Co2+ or Mn2+ to a 50-fold dilution of the denaturing medium. Titration of the denatured enzyme with either Co2+ or Mn2+ shows that wheat germ mutase preferentially binds Co2+. Assuming 1:1 complexation between metal atom and protein, the apparent dissociation constants (Kd) for E Co2+ and E Mn2+ at 22 degrees C and pH 8.7 are approximately 1.06 and 1.84, respectively. Other metal atoms (e.g., Cr2+, Cu2+, Fe2+, Fe3+, Mg2+, and Ni2+) have no effect in restoring the apoenzyme's catalytic activity. At low concentrations (0.11-0.23 mM) Zn2+ partially restores activity, but promotes protein precipitation at elevated concentrations. Evidence suggests that all bisphosphoglycerate-independent phosphoglycerate mutases require either an intra- or an extramolecular metal atom in order to function. Attempts to characterize wheat germ mutase as a glycoprotein have yielded negative results.
mesh_terms: D001731:Bisphosphoglycerate Mutase / Q000032:analysis*; D003035:Cobalt / Q000494:pharmacology; D019791:Guanidine; D006146:Guanidines; D007700:Kinetics; D008345:Manganese / Q000494:pharmacology; D010770:Phosphotransferases / Q000032:analysis*; D013997:Time Factors; D014908:Triticum / Q000201:enzymology*
chemical_list: D006146:Guanidines; D003035:Cobalt; D008345:Manganese; D010770:Phosphotransferases; D001731:Bisphosphoglycerate Mutase; D019791:Guanidine