Studies of the heme coordination and ligand binding properties of soluble guanylyl cyclase (sGC): characterization of Fe(II)sGC and Fe(II)sGC(CO) by electronic absorption and magnetic circular dichroism spectroscopies and failure of CO to activate the enzyme

Research on the heme coordination environment and ligand binding properties of ferrous bovine soluble guanylyl cyclase (Fe(II)sGC) and Fe(II)sGC(CO) reveals the axial liganding of histidine in Fe(II)sGC and the failure of CO to activate the enzyme. CO fails to activate the enzyme even though it binds to Fe(II)sGC hexacoordinately. Activation of sGC by nitric oxide can be made possible by breaking the bond between heme iron and histidine.