Specific glycosylation of 5-hydroxymethylcytosine (5-hmC) 5-hmC Glucosyltransferase catalyzes the transfer of a glucose moiety from uridine diphosphoglucose (UDPG) to existing 5-hmC in DNA to form glucosyl-5-hydroxymethylcytosine (glucosyl-5-hmC). 5-hmC Glucosyltransferase does not modify cytosines or methylated cytosines (5-mC). Glucosylation of 5-hmC can be used for sequence-specific, locus-specific, or global quantification of 5-hmC. Validation: 5-hmC Glucosyltransferase was incubated with three different DNA standards from the CpGenome 5-hmC and 5-mC DNA Standard Set (Cat. No. S8005), containing either 5-hmC, 5-mC, or no cytosine modifications. After glucosylation, the Standards were treated with CviQ1, a selective restriction endonuclease, which cleaves unmethylated, methylated, and hydroxymethylated DNA, but not glucosylated 5-hmC DNA. Agarose gel analysis of restriction digests showed a single band (undigested) only for the glycosylated 5-hmC Standard.