19F NMR studies on 8-fluoroflavins and 8-fluoro flavoproteins.
The 19F NMR spectra of the oxidized and reduced forms of 8-fluororiboflavin, 8-fluoro-FAD, and the 8-fluoroflavin-reconstituted flavoproteins flavodoxin, riboflavin binding protein, D-amino acid oxidase, p-hydroxybenzoate hydroxylase, Old Yellow Enzyme, anthranilate hydroxylase, general acyl-CoA dehydrogenase, glucose oxidase, and L-lactate oxidase were measured. For the proteins studied the oxidized resonances appeared over a 10.1-ppm range, while the reduced resonances were spread over 10.3 ppm. Reduction caused an upfield shift of about 27 ppm for the free 8-fluoroflavins and most of the 8-fluoro flavoproteins. The notable exception was 8-fluoro-FMN flavodoxin, which was shifted 37.6 ppm, indicating an unusually high electron density in the benzene ring. Ligand binding to the oxidized 8-fluoro flavoproteins caused either upfield or downfield shifts of 1.5-5 ppm, depending on the protein/ligand combination. The 8-fluoro-FAD anthranilate hydroxylase resonance was shifted downfield and split into two peaks in the presence of anthranilate. The 8-fluoro-FMN Old Yellow Enzyme resonance was shifted upfield upon complexation with charge-transfer-forming, para-substituted phenolates. The upfield shift increased from less than 1 to 5 ppm as the electron-donating capacity of the phenolate increased. Complexation of native Old Yellow Enzyme with 2,4-difluorophenol caused the fluorine resonances of the ligand to shift and split into two pairs of signals. Each pair of signals was associated with a different isozyme of Old Yellow Enzyme.
Macheroux
P
P
Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor 48109-0606.
Kojiro
C L
CL
Schopfer
L M
LM
Chakraborty
S
S
Massey
V
V
D044944:Acyl-CoA Dehydrogenases; D000818:Animals; D001059:Apoproteins; D001419:Bacteria / Q000201:enzymology; D003605:D-Amino-Acid Oxidase / Q000378:metabolism; D005415:Flavins; D005420:Flavoproteins; D005462:Fluorine Radioisotopes; D005466:Fluorocarbons; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D006899:Mixed Function Oxygenases; D015394:Molecular Structure; D062367:ortho-Aminobenzoates
D001059:Apoproteins; D005415:Flavins; D005420:Flavoproteins; D005462:Fluorine Radioisotopes; D005466:Fluorocarbons; D008024:Ligands; D062367:ortho-Aminobenzoates; D006899:Mixed Function Oxygenases; D044944:Acyl-CoA Dehydrogenases; D003605:D-Amino-Acid Oxidase