Glyceraldehyde 3-phosphate dehydrogenase (GAPDH), a key enzyme in carbohydrate metabolism, reversibly catalyzes the conversion of GAP to 1,3-bisphosphoglycerate and NAD+. Heptelidic acid is a sesquiterpene lactone produced by the fungus T. koningii that was shown to have antibiotic activity against anaerobic bacteria such as Bacteroides. It acts as an irreversible inhibitor of GAPDH that binds to the cysteine-149 residue at the active site of the enzyme (Ki = 1.6 ?M). It can selectively induce apoptosis in high-glycolytic cancer cells by inhibiting the generation of ATP in the glycolytic pathway. Heptelidic acid is also a selective and competitive inhibitor of mammalian DNA polymerases β and λ as well as terminal deoxynucleotidyl transferase in family X of DNA polymerases (Kis range from 5.2-9.5 ?M).