Nucleotide Regulation of Soluble Guanylate Cyclase Substrate Specificity

Soluble guanylate cyclase (sGC) serves as a receptor for the signaling agent nitric oxide (NO). sGC synthesis of cGMP is regulated by NO, GTP, ATP, and allosteric activators such as YC-1. The guanylate cyclase activity and adenylate cyclase activity of full-length sGC and the sGC catalytic domain constructs (alpha 1(cat)beta 1(cat)) are reported here. ATP is it mixed-type inhibitor of cGMP production for both sGC and alpha 1(cat)beta 1(cat), indicating that the C-terminus of sGC contains an allosteric nucleotide binding site. YC-1 did not activate alpha 1(cat)beta 1(cat), or compete with ATP inhibition ofcGMP synthesis, which suggests that YC-1 and ATP bind to distinct sites. alpha 1(cat)beta 1(cat), and NO-stimulated sGC also synthesize cAMP, but this activity is inhibited by ATP via noncompetitive substrate inhibition and by GTP via mixed-type inhibition. Additionally, the adenylate cyclase activity of purified sGC was inhibited by PC12 lysate, suggesting that an intracellular small molecule or protein regulates this activity in vivo.