Appearance of magnesium guanylate cyclase activity in rat liver with sodium azide activation.
Native soluble and particulate guanylate cyclase from several rat tissues preferred Mn2+ to Mg2+ as the sole cation cofactor. Wtih 4mM cation, activities with Mg2+ were less than 25% of the activities with Mn2+. The 1 mM NaN3 markedly increased the activity of soluble and particulate preparations from rat liver. Wtih NaN3 activation guanylate cyclase activities wite similar with Mn2+ and Mg2+. Co2+ was partially effective as a cofactor in the presence of NaN3, while Ca2+ was a poor cation with or without NaN3. Activities with Ba, Cu2+, or Zn2+ were not detectable without or with 1 mM NaN3. With soluble liver enzyme both manganese and magnesium activities were dependent upon excess Mn2+ or Mg2+ at a fixed MnGTP or MgGTP concentration of 0.4 mm; apparent Km values for excess Mn2+ and Mg2+ were 0.3 and 0.24 mM, respectively. After NaN3 activation, the activity was less dependent upon free Mn2+ and retained its dependence for free Mg2+, at 0.4 mM MgGTP the apparent Km for excess Mg2+ was 0.3 mM. The activity of soluble liver guanylate cyclase assayed with Mn2+ or Mg2+ was increased with Ca2+. After NaN3 activiation, Ca2+ had no effect or was somewhat inhibitory with either Mn2+. After NaN activation, Ca2+ had no effect or was somewhat inhibitory with either Mn2+ or Mg2+. The stimulatory effect of NaN2 on Mn2+-and Mg2+-dependent guanylate cyclase activity from liver or cerebral cortex supernatant fractions required the presence of the sodium azide-activator factor. With partially purified soluble liver guanylate cyclase and azide-activator factor, the concentration (1 mjM) of NaN3 that gave half-maximal activation with Mn2+ or Mg2+ was imilar. Thus, under some conditions guanylate cyclase can effectively use Mg2+ as a sole cation cofactor.
D000311:Adrenal Glands / Q000201:enzymology; D000818:Animals; D001386:Azides / Q000494:pharmacology*; D001921:Brain / Q000201:enzymology; D002413:Cations, Divalent; D004789:Enzyme Activation / Q000187:drug effects; D006162:Guanylate Cyclase / Q000302:isolation & purification / Q000378:metabolism*; D007668:Kidney / Q000201:enzymology; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology*; D008297:Male; D008345:Manganese / Q000494:pharmacology*; D009206:Myocardium / Q000201:enzymology; D009928:Organ Specificity; D010179:Pancreas / Q000201:enzymology; D051381:Rats
D001386:Azides; D002413:Cations, Divalent; D008345:Manganese; D006162:Guanylate Cyclase; D008274:Magnesium