Trypsin solubilization of rat liver membrane-bound guanylate cyclase results in a form kinetically distinct from the cytosolic enzyme
Haguenauer-Tsapis, R.; Ben Salah, A.; Lacombe, M.L.; Hanoune, J.
Journal of Biological Chemistry 256(4): 1651-1655
ISSN/ISBN: 0021-9258 PMID: 6109723 Accession: 044872323
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.