Zn2+, not Ca2+, is the most effective cation for activation of dolichol kinase of mammalian brain.
The cation specificity of dolichol kinase of mammalian brain and the potential involvement of a Ca2+-calmodulin system in regulation of this enzyme have been studied. Among 10 divalent cations examined, Zn2+ was found to be most effective for the activation of dolichol kinase of rat and calf brain and cultured C-6 glial cells. The activations with Ca2+, Co2+, and Mg2+ were 53%, 32%, and 18% of the full activation with Zn2+, respectively. No combinations of the cations could activate the enzyme as much as Zn2+ alone. A role for a Ca2+-calmodulin system in the regulation of brain dolichol kinase was not supported by our data. First, the concentration of free Ca2+ required for the maximum activation of dolichol kinase was two to three orders of magnitude greater than the concentration required by typical calmodulin-dependent enzymes. Second, neither the depletion of calmodulin from the microsomal fraction nor the addition of exogenous calmodulin caused an alteration in the activation of dolichol kinase by Ca2+ (or Zn2+). Third, antagonists of calmodulin failed to suppress the activation of the enzyme by Ca2+ (or Zn2+). The data raise the possibility that Zn2+ is involved in the regulation of dolichol kinase in brain.
D000818:Animals; D001921:Brain / Q000201:enzymology*; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism; D002417:Cattle; D002460:Cell Line; D004533:Egtazic Acid / Q000494:pharmacology; D004789:Enzyme Activation; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D008297:Male; D009457:Neuroglia / Q000201:enzymology; D010710:Phosphates / Q000378:metabolism; D010770:Phosphotransferases / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor); D051381:Rats; D011919:Rats, Inbred Strains; D015032:Zinc / Q000378:metabolism*
D002147:Calmodulin; D010710:Phosphates; D004533:Egtazic Acid; D010770:Phosphotransferases; D017853:Phosphotransferases (Alcohol Group Acceptor); C020087:dolichol kinase; D008274:Magnesium; D015032:Zinc; D002118:Calcium