Catalyzes the reductive methylation of 2'-deoxyuridine-5'-monophosphate (dUMP) to 2'-deoxythymidine-5'-monophosphate (dTMP) while utilizing 5,10-methylenetetrahydrofolate (mTHF) as the methyl donor and reductant in the reaction, yielding dihydrofolate (DHF) as a by-product (PubMed:3286637, PubMed:2223754, PubMed:9826509). This enzymatic reaction provides an intracellular de novo source of dTMP, an essential precursor for DNA biosynthesis. This protein also binds to its mRNA thus repressing its own translation (PubMed:7708505). (6R)-5,10-methylene-5,6,7,8-tetrahydrofolate + dUMP = 7,8-dihydrofolate + dTMP kcat is 8.8 sec(-1). Pyrimidine metabolism; dTTP biosynthesis. Homodimer. Although not discussed in the published references, Met-1 is represented in the submitted PDB entries as being modified by either a formyl, or a carboxyl group. The N-terminal is probably N-(dihydroxymethyl)methionine, the hydrated form of N-formylmethionine. Belongs to the thymidylate synthase family. Bacterial-type ThyA subfamily.