[Ferritin--a biocatalyst of aromatic amine oxidation].
The tetramethylbenzidine (TMB) oxidation kinetics dependent on spleen ferritin (FERR) has been studied in TMB-FERR-H2O2 (1) and TMB-FERR-O2 (2) systems at pH 4.2 and 6.0. At TMB concentrations below 6 mM, the dependencies of the initial rate for protein oxidation in system (1) on initial concentrations of TMB and H2O2 are described by the Michaelis-Menten kinetics. In terms of (kcat/K(m)), the maximum FERR efficiency during TMB oxidation is equal to 2.8-10(-1) s-1. Mannitol, urea, ethanol and sodium fluoride strongly inhibit TMB oxidation in system (1). Competitive type oxidation inhibition by urea is characterized by K(i) = 12.5 mM. At TMB concentrations above 6 mM in system (2) the autocatalytic oxidation of the amine is observed. In both systems the initial rate of TMB oxidation increases strongly with a decrease in pH from 9.3 down to 4.2. In system (1) the initiating role is played by Fe3+ ions interaction with H2O2, that in system (2)-by the interaction of the same ions with the amine proper. In both cases, TMB oxidation is a catalytic chain process including elementary ion radical stages. The main oxidizing agents in system (2) are HO radicals and Fe3+ ions. The TMB interaction with FERR may be the reason for the lipid peroxidation increase following administration of aromatic amines.
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D000818:Animals; D001560:Benzidines / Q000378:metabolism*; D002384:Catalysis; D000431:Ethanol / Q000378:metabolism; D005293:Ferritins / Q000502:physiology*; D006736:Horses; D006861:Hydrogen Peroxide / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008353:Mannitol / Q000378:metabolism; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D012969:Sodium Fluoride / Q000378:metabolism; D014508:Urea / Q000378:metabolism
D001560:Benzidines; C020515:N,N,N',N'-tetramethylbenzidine; D000431:Ethanol; D008353:Mannitol; D014508:Urea; D012969:Sodium Fluoride; D005293:Ferritins; D006861:Hydrogen Peroxide; D010100:Oxygen
Ferritin--blokatalizator okisleniia aromaticheskikh aminov.