Emission Spectroscopy of Complex Formation between Escherichia coli Purine Nucleoside Phosphorylase (PNP) and Identified Tautomeric Species of Formycin Inhibitors Resolves Ambiguities Found in Crystallographic Studies

Abstract

The ubiquitous purine nucleoside phosphorylases (PNPs) play a key role in the purine salvage pathway, and are widely considered as major targets in the chemotherapy of immune system diseases, as well as in potentiation of the antitumor and antiviral activities of therapeutically active nucleoside analogues, by preventing them from phosphorolytic cleavage. Therefore, wide attention is devoted to development of more potent and specific inhibitors of the enzyme from various sources, and to studies of the mechanism of enzyme action. This review recalls the results of studies by steadystate and time-resolved emission (fluorescence and phosphorescence) spectroscopy, X-ray crystallography and enzyme kinetics on the interaction of highly purified bacterial (E. coli) purine nucleoside phosphorylase with a specific formycin A inhibitor (antibiotic) and its N-methylated analogues. The red shift of absorption and emission spectra of the ligands versus the enzyme permits selective excitation of ligand in the enzyme-ligand complex, as well as selective detection of enzyme or ligand emission.KeywordsFluorescence Resonance Energy TransferTautomeric FormPurine Nucleoside PhosphorylaseTautomeric EquilibriumCopyright HolderThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.