The possibility that the spectrum of intermediate two, seen in the course of reaction of flavoenzyme phenol hydroxylases, may be attributable to iminol isomers of a flavin-derived 6-arylamino-5-oxo(3H,5H)uracil.
A commonly held view of the mechanism of flavin mixed-function oxidases is that enzyme-bound 4a-hydroperoxyflavin (4a-FIHOOH) undergoes ring opening to provide a carbonyl oxide (IV), which, after transferring an oxene equivalent to substrate, yields a 6-arylamino-5-oxo(3H,5H)-uracil (I). The latter is then thought to undergo ring closure to form a 4a-hydroxyflavin (4a-FIHOH), which by loss of water yields flavin (scheme I). A close structural analogue of I (i.e., III) has been synthesized. Comparison of the spectra of III (and II), taken in solvents of widely differing dielectric constants and in a strongly basic medium, with those of the intermediate(s) observed to be formed in time between 4a-FlHOOH and 4a-FlHOH has shown that the enzyme-bound intermediate(s) does not resemble spectrally I nor its iminol tautomers.
D005415:Flavins; D007536:Isomerism; D008745:Methylation; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D010084:Oxidation-Reduction; D013057:Spectrum Analysis; D014498:Uracil / Q000031:analogs & derivatives*
D005415:Flavins; C001922:lumiflavin; D014498:Uracil; D006899:Mixed Function Oxygenases; C022336:phenol 2-monooxygenase