Trypsin solubilization of rat liver membrane-bound guanylate cyclase results in a form kinetically distinct from the cytosolic enzyme.
We have previously reported that treatment of rat liver plasma membranes with various proteases led to activation and solubilization of membrane-bound guanylate cyclase. We report here that the guanylate cyclase solubilized by proteolysis differed from the cytosolic cyclase and rather was similar to the membrane-bound form of the enzyme in that it exhibited a sigmoidal MnGTP concentration dependence and was not activated by an excess Mn2+ or by nitrosocompounds. Also, whereas the cytosolic guanylate cyclase activity was completely abolished by 10 to 100 microM Cd2+, a dithiol reagent, no inhibitory effect was observed on the trypsin-solubilized enzyme. Therefore, the differences in kinetic properties between cytosolic and membrane-bound rat liver guanylate cyclase reside in structural differences between both forms of the enzyme rather than in differences in their environment.
D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D002462:Cell Membrane / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D006162:Guanylate Cyclase / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008345:Manganese / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D051381:Rats; D012995:Solubility; D014357:Trypsin
D002104:Cadmium; D009599:Nitroprusside; D008345:Manganese; D014357:Trypsin; D006162:Guanylate Cyclase