In enzymology, a deoxycytidylate 5-hydroxymethyltransferase () is an enzyme that catalyzes the chemical reaction
The 3 substrates of this enzyme are 5,10-methylenetetrahydrofolate, H<sub>2</sub>O, and deoxycytidylate, whereas its two products are tetrahydrofolate and 5-hydroxymethyldeoxycytidylate.
This enzyme belongs to the family of transferases that transfer one-carbon groups, specifically the hydroxymethyl-, formyl- and related transferases. The systematic name of this enzyme class is 5,10-methylenetetrahydrofolate:deoxycytidylate 5-hydroxymethyltransferase. Other names in common use include dCMP hydroxymethylase, d-cytidine 5'-monophosphate hydroxymethylase, deoxyCMP hydroxymethylase, deoxycytidylate hydroxymethylase, and deoxycytidylic hydroxymethylase. This enzyme participates in pyrimidine metabolism and one carbon pool by folate.
As of late 2007, 3 structures have been solved for this class of enzymes, with PDB accession codes , , and .