The sialic acids. X. Purification and properties of cytidine 5'-monophosphosialic acid synthetase.

An enzyme, cytidine monophosphate sialic acid synthetase, was purified from hog submaxillary glands. This enzyme (or enzymes) catalyzes the synthesis of CMP-N-acetylneuraminic acid or CMP-N-glycolylneuraminic acid or both and inorganic pyrophosphate from CTP and the corresponding sialic acids. The preparation was inactive with other known sialic acids and analogues of these compounds, and was also inactive with other nucleotides. The properties of the purified enzyme and its distribution are reported. Reversibility of the reaction was detected, i.e. the enzyme catalyzed the incorporation of 32PPi into CTP in complete incubation mixtures. Addition of hydroxylamine to incubation mixtures did not yield N-acetylneuraminic acid hydroxamate. The chemical synthesis of N-acetylneuraminic acid hydroxamate is described.