Catalyzes the fourth and sixth steps in the biosynthesis of pseudaminic acid, a sialic-acid-like sugar that is used to modify flagellin. The C-terminus mediates the fourth step of the pathway and catalyzes the removal of UDP from C-1 of UDP-2,4-diacetamido-2,4,6-trideoxy-beta-L-altropyranose forming 2,4-diacetamido-2,4,6-trideoxy-beta-L-altropyranose. The N-terminal part mediates the last step of the pathway by mediating activation of pseudaminic acid with CMP by forming CMP-pseudaminic acid. H2O + UDP-2,4-diacetamido-2,4,6-trideoxy-beta-L-altrose = 2,4-diacetamido-2,4,6-trideoxy-beta-L-altrose + H(+) + UDP CTP + pseudaminate = CMP-pseudaminate + diphosphate Mg(2+) is required for pseudaminic acid cytidylyltransferase activity. Monomer. In publications, PseF (HP_0326A) and PseG (HP_0326B) are separated into 2 separate ORFs (PubMed:16751642). However, these 2 enzymes are fused into a single protein in strain ATCC 700392 / 26695. In the N-terminal section; belongs to the CMP-NeuNAc synthase family. In the C-terminal section; belongs to the PseG family.