Effects of anions on the fluorescence emission of the 1-anilino-8-naphthalenesulfonate-phosphoglycerate kinase complex.

When 1-anilino-8-naphthalenesulfonate (ANS) interacts with phosphoglycerate kinase (ATP:3-phospho-D-glycerate 1-phosphotransferase, EC 2.7.2.3) its fluorescence is enhanced and a blue shift occurs. There is evidence that ANS binds to the site of the nucleotide substrate. The work described herein shows that when various anion inhibitors are added to the ANS-enzyme solution, de-enhancement of the fluorescence occurs. Extrapolation to infinite anion concentration shows that pyruvate ions are the most effective quenchers (ca. 90%) and nitrate ions the least effective, sulfate and phosphate ions being intermediate. The results are consistent with earlier enzymes kinetic findings suggesting that pyruvate ions and ANS, both competing with the nucleotide substrate, are able to bind to the enzyme simultaneously and that sulfate, phosphate and nitrate ions can, to various extents, affect the properties at the active centre of phosphoglycerate kinase via conformational changes without sharing ligands with the nucleotide substrate.