Inhibition of thymidylate synthase by glyceraldehyde 3-phosphate

1. A number of common metabolites which had carbonyl and/or phosphate groups were tested for their ability to alter the activity of thymidylate synthase from Lactobacillus casei. Glyceraldehyde 3-phosphate was found to be an effective inhibitor of thymidylate synthase. 2. Glyceraldehyde 3-phosphate reversibly inhibited thymidylate synthase with a K1 of 12-13 microM; the inhibition was competitive with dUMP and noncompetitive with 5,10-methylenetetrahydrofolate which is consistent with an ordered addition of substrates.