title: The stereochemical course of the reaction catalyzed by soluble bovine lung guanylate cyclase.
abstract: The stereochemical course of the reaction catalyzed by the soluble form of bovine lung guanylate cyclase has been investigated using [alpha-18O]guanosine 5'-triphosphate (Rp diastereomer) and guanosine 5'-O-(1-thiotriphosphate) (Sp diastereomer) as substrates. The product from the 3-thiomorpholino-1',1'-dioxide sydnonimine-stimulated enzymatic cyclization of [alpha-18O] guanosine 5'-triphosphate was esterified with diazomethane. 31P NMR analysis of the triesters indicated that all of the 18O label was present in the axial position. Guanosine 5'-O-(1-thiotriphosphate) (Sp diastereomer) was cyclized under stimulated and basal enzyme activities and, in both cases, the Rp diastereomer of guanosine 3',5'-cyclic phosphorothioate was formed. This was determined by direct comparison with material synthesized chemically from guanosine 5'-phosphorothioate. The results from these experiments show that the reaction catalyzed by guanylate cyclase proceeds with inversion of configuration at phosphorus and this indicates that the reaction proceeds by way of a single direct displacement reaction.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D003600:Cytosol / Q000201:enzymology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000031:analogs & derivatives*; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D006162:Guanylate Cyclase / Q000302:isolation & purification / Q000378:metabolism*; D008168:Lung / Q000201:enzymology*; D009682:Magnetic Resonance Spectroscopy; D011485:Protein Binding; D013237:Stereoisomerism; D013379:Substrate Specificity; D013873:Thionucleotides / Q000378:metabolism
chemical_list: D013873:Thionucleotides; C034882:guanosine 5'-O-(1-thiotriphosphate); D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D006162:Guanylate Cyclase