title: A magnesium-dependent guanylate cyclase in cell-free preparations of Dictyostelium discoideum.
abstract: Receptor-mediated regulation of guanylate cyclase is well-studied in intact Dictyostelium discoideum cells, but study of the enzyme in cell-free preparations has hampered. A major obstacle has been that in vitro guanylate cyclase activity could be detected only in the presence of unphysiological concentrations of Mn2+-ions. In this paper we report the identification of a guanylate cyclase in D.discoideum cell homogenates that has high activity with Mg2+-GTP. The enzyme is activated by non-hydrolyzable ATP and GTP analogues and inhibited by submicromolar concentrations of Ca2+-ions. We suggest that the presently identified enzyme is regulated in intact cells via cell surface receptors. The compounds that modulated the enzyme activity in vitro may reflect physiologically relevant regulation mechanisms.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000266:Adenylyl Imidodiphosphate / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D006152:Cyclic GMP / Q000096:biosynthesis; D004023:Dictyostelium / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology*; D008345:Manganese / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology
chemical_list: D013873:Thionucleotides; D000266:Adenylyl Imidodiphosphate; C036852:magnesium GTP; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D008345:Manganese; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D006162:Guanylate Cyclase; D006152:Cyclic GMP; D008274:Magnesium; D002118:Calcium