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Open AccessArticle

Catalase-Like Antioxidant Activity is Unaltered in Hypochlorous Acid Oxidized Horse Heart Myoglobin

1
Redox Biology Group, Discipline of Pathology, Faculty of Medicine and Health, Charles Perkins Centre, The University of Sydney, Sydney, NSW 2006, Australia
2
Discipline of Oral Pathology, Faculty of Medicine and Health, Charles Perkins Centre, The University of Sydney, Sydney, NSW 2006, Australia
*
Author to whom correspondence should be addressed.
Antioxidants 2019, 8(9), 414; https://doi.org/10.3390/antiox8090414
Received: 27 June 2019 / Revised: 27 August 2019 / Accepted: 16 September 2019 / Published: 18 September 2019
(This article belongs to the Section Aberrant Oxidation of Biomolecules)
Activated neutrophils release myeloperoxidase that produces the potent oxidant hypochlorous acid (HOCl). Exposure of the oxygen transport protein horse heart myoglobin (hhMb) to HOCl inhibits Iron III (Fe(III))-heme reduction by cytochrome b5 to oxygen-binding Iron II (Fe(II))Mb. Pathological concentrations of HOCl yielded myoglobin oxidation products of increased electrophoretic mobility and markedly different UV/Vis absorbance. Mass analysis indicated HOCl caused successive mass increases of 16 a.m.u., consistent serial addition of molecular oxygen to the protein. By contrast, parallel analysis of protein chlorination by quantitative mass spectrometry revealed a comparatively minor increase in the 3-chlorotyrosine/tyrosine ratio. Pre-treatment of hhMb with HOCl affected the peroxidase reaction between the hemoprotein and H2O2 as judged by a HOCl dose-dependent decrease in spin-trapped tyrosyl radical detected by electron paramagnetic resonance (EPR) spectroscopy and the rate constant of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) oxidation. By contrast, Mb catalase-like antioxidant activity remained unchanged under the same conditions. Notably, HOCl-modification of Mb decreased the rate of ferric-to-ferrous Mb reduction by a cytochrome b5 reductase system. Taken together, these data indicate oxidizing HOCl promotes Mb oxidation but not chlorination and that oxidized Mb shows altered Mb peroxidase-like activity and diminished rates of one-electron reduction by cytochrome b5 reductase, possibly affecting oxygen storage and transport however, Mb-catalase-like antioxidant activity remains unchanged. View Full-Text
Keywords: myoglobin; hypochlorous acid; protein oxidation; haem-iron reduction; MetMb reductase; catalase-like antioxidant activity myoglobin; hypochlorous acid; protein oxidation; haem-iron reduction; MetMb reductase; catalase-like antioxidant activity
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Ahmad, G.; Chami, B.; El Kazzi, M.; Wang, X.; Moreira, M.T.S.; Hamilton, N.; Maw, A.M.; Hambly, T.W.; Witting, P.K. Catalase-Like Antioxidant Activity is Unaltered in Hypochlorous Acid Oxidized Horse Heart Myoglobin. Antioxidants 2019, 8, 414.

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