uridylate

Uridylate, commonly referred to as uridine monophosphate (UMP), is the monophosphate ester of the nucleoside uridine. In RNA, uracil is linked to a ribose sugar, and in uridylate the sugar carries a single phosphate group at the 5' position. The molecule bears a negative charge under physiological conditions due to the phosphate group and forms the standard set of base-pairing interactions with adenine in RNA.

In cells, uridylate exists in three phosphorylated forms: UMP, UDP, and UTP, which are interconverted by specific kinases. UTP serves as a substrate for RNA synthesis by RNA polymerases and as a precursor for the generation of UDP-sugars used in glycosylation and polysaccharide biosynthesis. Uridylate can be generated de novo from orotate through the pyrimidine biosynthetic pathway, or salvaged from uracil by uracil phosphoribosyltransferase, combining PRPP with uracil to form UMP.

Biosynthesis and metabolism are tightly regulated to balance nucleotide pools needed for RNA production and other cellular processes. UMP is phosphorylated to UDP and then to UTP by nucleotide monophosphate and diphosphate kinases, respectively. UDP can also participate in other reactions, including the formation of UDP-sugars used in glycosylation reactions.

Biological significance: as a fundamental building block of RNA, uridylate is essential for transcription and RNA processing. In molecular biology, the term uridylation also refers to the addition of uridine residues to RNA ends by uridylyl transferases, a modification that can influence RNA stability and turnover.