Deoxycytidylate hydroxymethylase

Extracts of cells - of Escherichia coli infected with a T-even bacteriophage contain an enzyme deoxycytidylate hydroxymethylase which is not detected in uninfected cells it catalyzes the formation of 6 -(hydroxymethyl)-2-deoxyc3didylic acid from formaldehyde and 2-deoxycytidyUc acid in the presence of tetrahydrofolic acid and magnesium ions. In a large-scale experiment, 10.6 mg. of the barium salt was prepared. 

The synthesis of 5-hydroxymethyldeoxycytidylate should be mentioned at this point, because this process is similar in many respects to the thymidylate synthetase reaction. The enzyme responsible, termed deoxycytidylate hydroxymethylase, catalyzes an H4-folate-dependent introduction of a hydroxymethyl group into the 5-position of deoxycytidylate. 

The hydroxymethylase activity cannot be detected in uninfected E. coli. It may be noted that this reaction differs from thymidylate synthesis in that a reduction is not involved, as indicated by the fact that H -folate is a product. In studies of the mechanism of the reaction catalyzed by the the T4-induced hydroxymethylase, Yeh and Greenberg IS) have shown that tritium is displaced from deoxycytidylate-5- H with the formation of product. As well, the enzyme catalyzed an H4-folate-dependent exchange between water and the hydrogen atom at the 5-position of dCMP. 

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