The Guanylyl Cyclase Core of an Atrial Natriuretic Peptide Receptor: Enzymatic Properties and Basis for Cooperativity

The enzymatic properties of a cloned atrial natriuretic peptide receptor are described. The renatured catalytic core had maximal activity with Mn2+, and all nucleoside triphosphates inhibited the enzyme competitively. The catalytic specificity of the enzyme was tested directly. The cyclase reaction was specific for guanine, producing cGMP and cyclic deoxyGMP. Surprisingly, deoxyguanylyl cyclase kinetics were classical, unlike the positive cooperativity seen for guanylyl cyclase activity, suggesting that the 2′ hydroxyl group of GTP is necessary for the allosteric mechanism.