title: Magnesium-sensitive guanylate cyclase and its endogenous activating factor in Tetrahymena pyriformis.
abstract: Guanylate cyclase [EC 4.6.1.2] activity in Tetrahymena pyriformis cells was associated with particulate fractions, but not with soluble fractions. Mg2+ was much more effective than Mn2+ in activating the cyclase activity. Both specific and total cyclase activities with Mg2+ in the particulate fraction were very much lower than those in the original homogenate. The addition of the soluble fraction resulted in a marked enhancement of the particulate-bound cyclase activity, while the adenylate cyclase [EC 4.6.1.1] activity was not enhanced. The enhancement was dependent on Ca2+, and the activating factor is suggested to be a protein.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004789:Enzyme Activation; D006162:Guanylate Cyclase / Q000378:metabolism*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology*; D008345:Manganese / Q000494:pharmacology; D011506:Proteins / Q000502:physiology*; D013769:Tetrahymena pyriformis / Q000201:enzymology*; D014357:Trypsin / Q000494:pharmacology
chemical_list: D011506:Proteins; D008345:Manganese; D004533:Egtazic Acid; D014357:Trypsin; D006162:Guanylate Cyclase; D008274:Magnesium; D002118:Calcium