Mechanism of aromatic hydroxylation. Properties of a model for pyridine nucleotide-dependent flavoprotein hydroxylases

S. D. Ravindranath, A. Ashok Kumar, R. Prema Kumar, C. S. Vaidyanathan, N. Appaji Rao

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

A model (NADH-phenazine methosulfate-O2) formally similar to pyridine nucleotide-dependent flavoprotein hydroxylases catalyzed the hydroxylation of several aromatic compounds. The hydroxylation was maximal at acid pH and was inhibited by ovine Superoxide dismutase, suggesting that perhydroxyl radicals might be intermediates in this process. The stoichiometry of the reaction indicated that a univalent reduction of oxygen was occurring. The correlation between the concentration of semiquinone and hydroxylation, and the inhibition of hydroxylation by ethanol which inhibited semiquinone oxidation, suggested the involvement of phenazine methosulfate-semiquinone. Activation of hydroxylation by Fe3+ and Cu2+ supported the contention that univalently reduced species of oxygen was involved in hydroxylation. Catalase was without effect on the hydroxylation by the model, ruling out H2O2 as an intermediate. A reaction sequence, involving a two-electron reduction of phenazine methosulfate to reduced phenazine methosulfate followed by disproportionation with phenazine methosulfate to generate the semiquinone, was proposed. The semiquinone could donate an electron to O2 to generate O2 which could be subsequently protonated to form the perhydroxyl radical.

Original languageEnglish
Pages (from-to)478-484
Number of pages7
JournalArchives of Biochemistry and Biophysics
Volume165
Issue number2
DOIs
Publication statusPublished - 01-01-1974

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Flavoproteins
Hydroxylation
Methylphenazonium Methosulfate
Mixed Function Oxygenases
Nucleotides
Electrons
Oxygen
Aromatic compounds
pyridine
Stoichiometry
NAD
Catalase
Superoxide Dismutase
Sheep
Ethanol
Chemical activation
Oxidation
Acids

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Biochemistry
  • Molecular Biology

Cite this

Ravindranath, S. D. ; Kumar, A. Ashok ; Kumar, R. Prema ; Vaidyanathan, C. S. ; Rao, N. Appaji. / Mechanism of aromatic hydroxylation. Properties of a model for pyridine nucleotide-dependent flavoprotein hydroxylases. In: Archives of Biochemistry and Biophysics. 1974 ; Vol. 165, No. 2. pp. 478-484.
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Mechanism of aromatic hydroxylation. Properties of a model for pyridine nucleotide-dependent flavoprotein hydroxylases. / Ravindranath, S. D.; Kumar, A. Ashok; Kumar, R. Prema; Vaidyanathan, C. S.; Rao, N. Appaji.

In: Archives of Biochemistry and Biophysics, Vol. 165, No. 2, 01.01.1974, p. 478-484.

Research output: Contribution to journalArticle

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