CMPsialic

CMPsialic, more commonly called CMP-sialic acid (CMP-Neu5Ac), is the activated donor form of the monosaccharide sialic acid used in the biosynthesis of sialoglycans. It serves as the substrate for sialyltransferase enzymes that decorate proteins and lipids with terminal sialic acid residues, influencing cell–cell interactions, signaling, and stability of glycoproteins and glycolipids.

Biosynthesis begins with sialic acid (N-acetylneuraminic acid, Neu5Ac). Neu5Ac is activated by cytidine triphosphate (CTP) through the enzyme CMP-sialic acid synthetase (CMAS) to form CMP-Neu5Ac. In vertebrates, CMAS activity is primarily nuclear, and the resulting CMP-Neu5Ac is transported into the Golgi lumen by the CMP-sialic acid transporter SLC35A1. Once inside the Golgi, sialyltransferases transfer Neu5Ac from CMP-Neu5Ac to the growing glycan chains on glycoproteins and glycolipids.

Function and significance are tied to the proper sialylation of glycoconjugates. Sialylation affects protein half-life, receptor binding, immune recognition, and cell adhesion. Defects in CMP-Neu5Ac synthesis, transport, or transfer can contribute to congenital disorders of glycosylation and related diseases. In biotechnology and medicine, engineering CMP-Neu5Ac pathways can modulate the sialylation and pharmacokinetics of therapeutic proteins. CMP-sialic thus occupies a central role in the regulation of glycan structures across tissues.