Flavin-dependent thymidylate synthase

UniProtKB accession:  Q9WYT0

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UniProtKB description:  Catalyzes the reductive methylation of 2'-deoxyuridine-5'-monophosphate (dUMP or deoxyuridylate) to 2'-deoxythymidine-5'-monophosphate (dTMP or deoxythymidylate) while utilizing 5,10-methylenetetrahydrofolate (mTHF) as the methylene donor, and NAD(P)H and FADH(2) as the reductant. This reaction is a critical step in DNA biosynthesis (PubMed:12791256, PubMed:19370033). Can also use formaldehyde instead of mTHF as a direct methylene donor for dTMP synthesis. However, the tighter binding of ThyX to mTHF (KD of 4 uM) compared to formaldehyde (KD of 20 mM) confirms that methylene tetrahydrofolate acts as the biological carbon donor for ThyX, serving as a formaldehyde carrier/transporter and thus avoiding genotoxic effects (PubMed:34315871).