Involved in the biosynthesis of the O-methyl phosphoramidate (MeOPN) group found on the capsular polysaccharide (CPS) of C.jejuni (PubMed:17675288). Catalyzes the ATP-dependent phosphorylation of cytidine diphosphoramidate (CDP-NH(2)) to form cytidine 3'-phosphate 5'-diphosphoramidate (PubMed:29578334). Can also use other substrates such as the corresponding adenine and uridine diphosphoramidate derivatives or cytidine diphosphoramidate analogs, with lower efficiency (PubMed:29578334). ATP + cytidine 5'-diphosphoramidate = ADP + cytidine 3'-phospho-5'-diphosphoramidate + H(+) kcat is 2.2 sec(-1) with cytidine diphosphoramidate as substrate. kcat is 2.2 sec(-1) with 2'-deoxycytidine diphosphoramidate as substrate. kcat is 0.64 sec(-1) with CDP as substrate. kcat is 0.65 sec(-1) with CDP-methyl phosphate as substrate. kcat is 1.4 sec(-1) with CDP-methyl phosphonate as substrate. kcat is 0.023 sec(-1) with uridine diphosphoramidate as substrate. kcat is 0.08 sec(-1) with adenosine diphosphoramidate as substrate. Capsule biogenesis; capsule polysaccharide biosynthesis. Mutant does not express the MeOPN CPS modification. Belongs to the APS kinase family.