title: Subcellular distribution and some properties of particulate guanylate cyclase of pigeon myocardium.
abstract: Most of the particle-bound guanylate cyclase of pigeon heart muscle, which is the predominant form of the enzyme in this tissue, co-purified with calcium pump system of the sarcoplasmic reticular fraction. Specific enzyme activity at 37 degrees C ranged up to 0.67 nmol/mg of protein/min. The K0.5 values for MnCl2, Mn2+ free, and GTP were found to be 0.72, 0.076, and 0.057 mM, respectively. Mg2+ activates and Ca2+ inhibits the enzyme in the presence of Mn2+, whereas carbamylcholine was without effect. The ratio of guanylate cyclase to adenylate cyclase activity was found to be 12:1 in the sarcoplasmic reticulum fraction and 0.5:1 in the sarcolemal fraction. Our findings suggest that the major portion of guanylate cyclase in pigeon myocardium is not directly activated by the interaction of hormones and neurotransmitters with their receptors in the cell surface membrane.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D010856:Columbidae; D006162:Guanylate Cyclase / Q000378:metabolism; D008345:Manganese; D008861:Microsomes / Q000201:enzymology; D009206:Myocardium / Q000201:enzymology*; D012519:Sarcoplasmic Reticulum / Q000201:enzymology; D013347:Subcellular Fractions
chemical_list: D008345:Manganese; D000262:Adenylyl Cyclases; D006162:Guanylate Cyclase