The role of phosphate in the action of thymidine phosphorylase inhibitors: Implications for the catalytic mechanism

Bioorg Med Chem Lett. 2010 Mar 1;20(5):1648-51. doi: 10.1016/j.bmcl.2010.01.076. Epub 2010 Jan 21.

Abstract

The design and synthesis of 5-fluoro-6-[(2-aminoimidazol-1-yl)methyl]uracil (AIFU), a potent inhibitor of thymidine phosphorylase (TP) with K(i)-values of 11nM (ecTP) and 17nM (hTP), are described. Kinetic studies established that the type of inhibition of TP by AIFU is uncompetitive with respect to inorganic phosphate (or arsenate). The results obtained suggest that AIFU and other zwitterionic thymine analog inhibitors of TP act as transition state analogs, mimicking the anionic thymine leaving group, consistent with an S(N)2-type catalytic mechanism, and anchored by their protonated side chains to the enzyme-bound phosphate by electrostatic and H-bonding interactions.

MeSH terms

  • Catalysis
  • Catalytic Domain
  • Enzyme Inhibitors / chemistry*
  • Hydrogen Bonding
  • Kinetics
  • Phosphates / chemistry*
  • Protein Binding
  • Static Electricity
  • Thymidine Phosphorylase / antagonists & inhibitors*
  • Thymidine Phosphorylase / metabolism
  • Thymine / analogs & derivatives
  • Thymine / chemistry
  • Thymine / pharmacology

Substances

  • Enzyme Inhibitors
  • Phosphates
  • Thymidine Phosphorylase
  • Thymine