Open AccessThe 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.
Author(s) -
Albert Wessiak,
J. Barry Noar,
Thomas C. Bruice
Publication year - 1984
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.81.2.332
Subject(s) - flavin group , tautomer , chemistry , ring (chemistry) , photochemistry , substrate (aquarium) , uracil , stereochemistry , computational chemistry , enzyme , dna , organic chemistry , biochemistry , oceanography , geology
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.