part of cyclic nucleotide biosynthetic process cyclase activity phosphorus-oxygen lyase activity cytidylate cyclase activity https://github.com/geneontology/go-ontology/issues/30193 cytidyl cyclase activity CTP diphosphate-lyase (cyclizing) CTP diphosphate-lyase (cyclizing; 3',5'-cyclic-CMP-forming) EC:4.6.1.6 3'5'-cyclic-CMP synthase activity RHEA:14737 MetaCyc:CYTIDYLATE-CYCLASE-RXN molecular_function GO:0047805 3',5'-cyclic-CMP synthase activity KEGG_REACTION:R00574 Catalysis of the reaction: CTP = 3',5'-cyclic CMP + diphosphate + H+. cytidylyl cyclase activity