Abstract
The oxidation of ascorbic acid by air oxygen and hydrogen peroxide in the presence of the copper-binding compound (cbc) from bacteria Methylococcus capsulatus (M) was studied. The rate constant of ascorbic acid oxidation by air oxygen in the presence of the copper complex with cbc from M. capsulatus (M) was shown to be 1.5 times higher than that of the noncatalytic reaction. The rate constant of ascorbic acid oxidation by hydrogen peroxide in the presence of the copper complex with cbc from M. capsulatus (M) decreased by almost one-third compared to the reaction in the absence of the copper complex with cbc. It was assumed that cbc can be involved in a multilevel system of antioxidant protection and can protect a bacterial cell from oxidation stress. Thus, the cbc is mimetic ascorbate oxidase in the oxidation of ascorbic acid by molecular oxygen.
Highlights
Methanotrophic bacteria use methane as a source of carbon and energy and participate in the global carbon cycle
Biological metabolism of methane starts from the activation of the inert C–H bond of methane catalyzed by methane monooxygenase (MMO)
The purpose of this work is to study of the redox active properties of the cbc from Methylococcus capsulatus (M), in particular in the oxidation reaction of L-ascorbic acid (H2 A) in order to highlight the properties of the cbc for understanding its function in methane oxidation by pMMO and possible participation in the antioxidant system of methanotrophs
Summary
Methanotrophic bacteria (methanotrophs) use methane as a source of carbon and energy and participate in the global carbon cycle. There are two types of methane monooxygenase: soluble (sMMO) and particulate (pMMO). An interrelation is observed between the copper concentration and the expression of two monooxygenases. Methanotrophs are widely abundant in nature and live under various conditions. Changes in external factors lead to a series of consequences for a bacterial cell, in particular, in an increase in the level of reactive oxygen species (ROS) in the cell, among which are superoxide (O2 − ), singlet oxygen, hydrogen peroxide (H2 O2 ), hydroxyl radical (OH− ), and others. Hydrogen peroxide is the most stable of the intermediate products of oxygen reduction but is the least reactive one. It is known that hydrogen peroxide is a reversible inhibitor for pMMO from Methylosinus trichosporium OB3b under anaerobic conditions [2]
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