Involved in the biosynthesis of the O-methyl phosphoramidate (MeOPN) group found on the capsular polysaccharide (CPS) of C.jejuni (PubMed:17675288). Catalyzes the hydrolysis of CDP-L-glutamine to L-glutamate and cytidine diphosphoramidate (PubMed:29023101). H2O + N(5)-(cytidine 5'-diphosphoramidyl)-L-glutamine = cytidine 5'-diphosphoramidate + H(+) + L-glutamate kcat is 34 min(-1). Capsule biogenesis; capsule polysaccharide biosynthesis. Mutant does not express the MeOPN CPS modification.