Involved in the biosynthesis of the O-methyl phosphoramidate (MeOPN) group found on the capsular polysaccharide (CPS) of C.jejuni (PubMed:17675288). Catalyzes the formation of CDP-L-glutamine from CTP and L-glutamine phosphate (PubMed:29023101, PubMed:30929435). In the presence of MnCTP, catalyzes the displacement of pyrophosphate from CTP using phosphoramidate, methyl phosphate, methyl phosphonate, phosphate, arsenate, ethanolamine phosphate, (R/S)-glycerol-1-phosphate, glycerol-2-phosphate, serinol phosphate, L-serine phosphate and 3-phospho-D-glycerate as substrate in addition to L-glutamine phosphate (PubMed:30929435). CTP + H(+) + N(5)-phospho-L-glutamine = diphosphate + N(5)-(cytidine 5'-diphosphoramidyl)-L-glutamine kcat is 57 min(-1) with L-glutamine phosphate as substrate (in the presence of MgCTP) (PubMed:29023101). kcat is 0.35 min(-1) with L-glutamine phosphate as substrate (in the presence of MnCTP). kcat is 0.6 min(-1) with phosphoramidate as substrate (in the presence of MnCTP). kcat is 3.7 min(-1) with 3-phospho-D-glycerate as substrate (in the presence of MnCTP). kcat is 0.18 min(-1) with phosphate as substrate (in the presence of MnCTP). kcat is 0.07 min(-1) with methyl phosphate as substrate (in the presence of MnCTP). kcat is 0.15 min(-1) with methyl phosphonate as substrate (in the presence of MnCTP). kcat is 0.18 min(-1) with arsenate as substrate (in the presence of MnCTP). kcat is 0.017 min(-1) with ethanolamine phosphate as substrate (in the presence of MnCTP). kcat is 0.07 min(-1) with (R/S)-glycerol-1-phosphate as substrate (in the presence of MnCTP). kcat is 0.08 min(-1) with glycerol-2-phosphate as substrate (in the presence of MnCTP). kcat is 0.017 min(-1) with serinol phosphate as substrate (in the presence of MnCTP). kcat is 0.18 min(-1) with L-serine phosphate as substrate (in the presence of MnCTP) (PubMed:30929435). Capsule biogenesis; capsule polysaccharide biosynthesis. Mutant does not express the MeOPN CPS modification. This enzyme is able to catalyze reactions that produce natural compounds CDP-ethanolamine, CDP-1-glycerol and CDP-2-glycerol, two of which are not available commercially. It can also produce CDP-serine, CDP-serinol and CDP-3-D-glycerate which may be potential inhibitors or mechanistic probes for enzymes that use CDP-glycerol. The labeled nucleotides, such as beta-[(18)O4]-CDP, generated with this enzyme can be used to probe the details of enzyme-catalyzed reactions using positional isotope exchange (PIX) and molecular isotope exchange (MIX) techniques.