Abstract
AbstractChlorite dismutase is a heme enzyme that catalyzes the conversion of the toxic compound ClO2−(chlorite) to innocuous Cl−and O2. The reaction is a very rare case of enzymatic O–O bond formation, which has sparked the interest to elucidate the reaction mechanism using pre-steady-state kinetics. During stopped-flow experiments, spectroscopic and structural changes of the enzyme were observed in the absence of a substrate in the time range from milliseconds to minutes. These effects are a consequence of illumination with UV–visible light during the stopped-flow experiment. The changes in the UV–visible spectrum in the initial 200 s of the reaction indicate a possible involvement of a ferric superoxide/ferrous oxo or ferric hydroxide intermediate during the photochemical inactivation. Observed EPR spectral changes after 30 min reaction time indicate the loss of the heme and release of iron during the process. During prolonged illumination, the oligomeric state of the enzyme changes from homo-pentameric to monomeric with subsequent protein precipitation. Understanding the effects of UV–visible light illumination induced changes of chlorite dismutase will help us to understand the nature and mechanism of photosensitivity of heme enzymes in general. Furthermore, previously reported stopped-flow data of chlorite dismutase and potentially other heme enzymes will need to be re-evaluated in the context of the photosensitivity.Graphic abstractIllumination of recombinantly expressedAzospira oryzaeChlorite dismutase (AoCld) with a high-intensity light source, common in stopped-flow equipment, results in disruption of the bond between FeIIIand the axial histidine. This leads to the enzyme losing its heme cofactor and changing its oligomeric state as shown by spectroscopic changes and loss of activity.
Funder
Nederlandse Organisatie voor Wetenschappelijk Onderzoek
Delft University of Technology
Publisher
Springer Science and Business Media LLC
Subject
Inorganic Chemistry,Biochemistry
Cited by
5 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献