cytidylyltransferases

Cytidylyltransferases are enzymes that catalyze the transfer of a cytidylyl group from cytidine triphosphate (CTP) to an acceptor molecule, forming cytidylylated products such as CDP-sugars or CDP-containing lipids and releasing pyrophosphate. They belong to the nucleotidyltransferase family and act on a variety of substrates including sugars, lipids, and small metabolites. The general reaction can be summarized as CTP + acceptor-OH → CMP-acceptor + PPi, with the CMP moiety transferred to the acceptor to activate it for further biosynthetic steps.

Key members include CTP:phosphocholine cytidylyltransferase, which generates CDP-choline in the Kennedy pathway for phosphatidylcholine synthesis; CDP-diacylglycerol synthase, which produces CDP-diacylglycerol, a central carrier for glycerophospholipid and cardiolipin biosynthesis; and glucose-1-phosphate cytidylyltransferase, which yields CDP-glucose for glycoconjugate and polysaccharide biosynthesis. In bacteria and archaea, cytidylyltransferases participate in the production of CDP-activated sugars required for capsule, lipopolysaccharide, and extracellular polysaccharide assembly.

Biochemical properties: these enzymes often require divalent metal ions such as Mg2+ and function via typical nucleotidyl transfer mechanisms. Many cytidylyltransferases are associated with membranes or membrane synthesis pathways, and they can be regulated by substrate availability and cellular lipid composition.

Significance: cytidylyltransferases are essential for generating activated intermediates used in membrane biosynthesis and glycan assembly. They are of interest in biotechnology and antimicrobial research, as pathway alterations can affect cell envelope construction and virulence in pathogens.