Identification and properties of 8-hydroxyflavin--adenine dinucleotide in electron-transferring flavoprotein from Peptostreptococcus elsdenii.
1. A new flavin prosthetic group has been isolated in pure form from the electron-transferring flavoprotein of Peptostreptococcus elsdenni. Its structure has been established as the FAD derivative of 7-methyl-8-hydroxyisoalloxazine: (see article). Proof of this structure has been obtained by chemical syntehsis of 7-methyl-8-hydroxyisoalloxazine models, and by stepwise degradation of the native compound to 7-methy-8-hydroxyalloxazine. The orange chromophore is characterized by a strong absorption band with a maximum at 472 nm (xi = 41 000 M-1 CM-1) and a pK at 4.8 due to the ionisation of the C(8)-OH group. 2. The properties of a series of functionally substituted derivatives of 8-hydroxy flavins and lumichromes have been investigated to provide a basis for interpreting the effects of pH on the spectroscopic properties of the 8-hydroxy derivatives of FAD and FMN. 3. The 8-hydroxy derivative of FAD is bound by apo-D-amino acid oxidase; the complex shows no catalytic activity. The 8-hydroxy derivative of FMN is bound by apoflavodoxin to give a complex which has catalytic activity similar to that of native flavodoxin. The complex is reversibly reduced by dithionite, first to a relatively stable semiquinone and further to the dihydroflavin form.
D001665:Binding Sites; D002854:Chromatography, Paper; D004590:Electrophoresis, Paper; D005182:Flavin-Adenine Dinucleotide / Q000031:analogs & derivatives* / Q000032:analysis; D005415:Flavins / Q000032:analysis / Q000138:chemical synthesis; D005420:Flavoproteins; D006863:Hydrogen-Ion Concentration; D010462:Peptostreptococcus / Q000032:analysis*; D011485:Protein Binding; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D013329:Structure-Activity Relationship
D005415:Flavins; D005420:Flavoproteins; D005182:Flavin-Adenine Dinucleotide