JBC, Vol. 250, Issue 16, 6214-6217, Aug, 1975
Guanylate cyclase in Escherichia coli. Purification and properties
V. Macchia, S. Varrone, H. Weissbach and D. L. Miller
Guanylate cyclase has been purified from extracts of Escherichia coli.
After a 1000-fold purification, the enzyme contains only minor contaminants
as judged by disc gel electrophoresis. The Km for GTP is approximately 7
times 10(-5) M and the optimal pH is 8.0. More activity is observed with
Mn2+ than with Mg2+, and maximal activity is observed at 0.14 mM Mn2+ and
1.4 mM Mg2+. Based on its behavior on Sephadex G-100, the molecular weight
of E. coli guanylate cyclase is about 30,000. Disc gel electrophoretic
analysis indicates that the enzyme consists of a single polypeptide chain.
Guanylate cyclase does not form 3':5'-AMP from ATP, and therefore, is
distinct from adenylate cyclase.