Positive cooperativity in substrate binding by human thymidylate synthase (Biophysical Journal)

Thymidylate synthase (TS) catalyzes the production of the nucleotide dTMP from dUMP, making the enzyme necessary for DNA replication and consequently a target for cancer therapeutics. TSs are homodimers with active sites separated by ~30 Å. Reports of half-the-sites activity in TSs from multiple species demonstrate the presence of allosteric communication between the active sites of this enzyme. A simple explanation for the negative allosteric regulation occurring in half-the-sites activity would be that the two substrates bind with negative cooperativity.