Stability and Catalase-Like Activity of a Mononuclear Non-Heme Oxoiron(IV) Complex in Aqueous Solution.

Publisher: MDPI Country of Publication: Switzerland NLM ID: 100964009 Publication Model: Electronic Cited Medium: Internet ISSN: 1420-3049 (Electronic) Linking ISSN: 14203049 NLM ISO Abbreviation: Molecules Subsets: MEDLINE

Original Publication: Basel, Switzerland : MDPI, c1995-

Catalase/*chemistry ; Heme/*chemistry ; Iron/*chemistry; Enzyme Activation ; Hydrogen Peroxide/chemistry ; Molecular Structure ; Oxidation-Reduction ; Solutions

Competing Interests: The authors declare no conflict of interest.
Heme-type catalase is a class of oxidoreductase enzymes responsible for the biological defense against oxidative damage of cellular components caused by hydrogen peroxide, where metal-oxo species are proposed as reactive intermediates. To get more insight into the mechanism of this curious reaction a non-heme structural and functional model was carried out by the use of a mononuclear complex [Fe ^II (N4Py*)(CH 3 CN)](CF 3 SO 3 ) 2 (N4Py* = N , N -bis(2-pyridylmethyl)- 1,2-di(2-pyridyl)ethylamine) as a catalyst, where the possible reactive intermediates, high-valent Fe ^IV =O and Fe ^III -OOH are known and spectroscopically well characterized. The kinetics of the dismutation of H 2 O 2 into O 2 and H 2 O was investigated in buffered water, where the reactivity of the catalyst was markedly influenced by the pH, and it revealed Michaelis-Menten behavior with K M = 1.39 M, k cat = 33 s ^-1 and k 2 (k cat /K M ) = 23.9 M ^-1 s ^-1 at pH 9.5. A mononuclear [(N4Py)Fe ^IV =O] ²⁺ as a possible intermediate was also prepared, and the pH dependence of its stability and reactivity in aqueous solution against H 2 O 2 was also investigated. Based on detailed kinetic, and mechanistic studies (pH dependence, solvent isotope effect (SIE) of 6.2 and the saturation kinetics for the initial rates versus the H 2 O 2 concentration with K M = 18 mM) lead to the conclusion that the rate-determining step in these reactions above involves hydrogen-atom transfer between the iron-bound substrate and the Fe(IV)-oxo species.

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Keywords: catalase activity; hydrogen peroxide; iron(IV)-oxo; kinetic studies; oxidation

0 (Solutions)
42VZT0U6YR (Heme)
BBX060AN9V (Hydrogen Peroxide)
E1UOL152H7 (Iron)
EC 1.11.1.6 (Catalase)

Date Created: 20190908 Date Completed: 20200127 Latest Revision: 20200127

20250114

PMC6766873

10.3390/molecules24183236

31491998