J. Biol. Chem., Vol. 256, Issue 4, 1651-1655, 02, 1981
Trypsin solubilization of rat liver membrane-bound guanylate cyclase results in a form kinetically distinct from the cytosolic enzyme
R Haguenauer-Tsapis, A Ben Salah, ML Lacombe and J Hanoune
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.
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