A chemical model for the thymidylate synthetase catalysed methylation of deoxyuridine monophosphate

Abstract

In a study of a model for the reaction catalysed by the enzyme thymidylate synthetase, a compound previously thought to be the putative intermediate 5-(uracil-5-ylmethyl)tetrahydropteroylglutamic acid (4b) has been prepared and shown to be the 5,10-bis(uracil-5-ylmethyl) adduct (4c). The tetrahydrofolic acid adduct (4d) and its [6-²H₁] analogue have been prepared and have been shown to be thermally converted into thymine (5, R²= H). The reaction with deuteriated (4d) shows a high discrimination for the hydrogen at C-6 of the pteridine moiety which rearranges to the methyl group of the resultant thymine (5, R²= H). These findings parallel results found for the biochemical process very closely and possible mechanisms for the reaction are discussed. The compounds (4c) and (4d) are neither substrates nor inhibitors of thymidylate synthetase.