Hypochlorite-induced oxidation of proteins in plasma: formation of chloramines and nitrogen-centred radicals and their role in protein fragmentation
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Hypochlorite-induced oxidation of proteins in plasma : formation of chloramines and nitrogen-centred radicals and their role in protein fragmentation. / Hawkins, C L; Davies, Michael Jonathan.
In: Biochemical Journal, Vol. 340 ( Pt 2), 01.06.1999, p. 539-48.Research output: Contribution to journal › Journal article › peer-review
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TY - JOUR
T1 - Hypochlorite-induced oxidation of proteins in plasma
T2 - formation of chloramines and nitrogen-centred radicals and their role in protein fragmentation
AU - Hawkins, C L
AU - Davies, Michael Jonathan
PY - 1999/6/1
Y1 - 1999/6/1
N2 - Activated phagocyte cells generate hypochlorite (HOCl) via the release of H2O2 and the enzyme myeloperoxidase. Plasma proteins are major targets for HOCl, although little information is available about the mechanism(s) of oxidation. In this study the reaction of HOCl (at least 50 microM) with diluted fresh human plasma has been shown to generate material that oxidizes 5-thio-2-nitrobenzoic acid; these oxidants are believed to be chloramines formed from the reaction of HOCl with protein amine groups. Chloramines have also been detected with isolated plasma proteins treated with HOCl. In both cases chloramine formation accounts for approx. 20-30% of the added HOCl. These chloramines decompose in a time-dependent manner when incubated at 20 or 37 degrees C but not at 4 degrees C. Ascorbate and urate remove these chloramines in a time- and concentration-dependent manner, with the former being more efficient. The reaction of fresh diluted plasma with HOCl also gives rise to protein-derived nitrogen-centred radicals in a time- and HOCl-concentration-dependent manner; these have been detected by EPR spin trapping. Identical radicals have been detected with isolated HOCl-treated plasma proteins. Radical formation was inhibited by excess methionine, implicating protein-derived chloramines (probably from lysine side chains) as the radical source. Plasma protein fragmentation occurs in a time- and HOCl-concentration-dependent manner, as evidenced by the increased mobility of the EPR spin adducts, the detection of further radical species believed to be intermediates in protein degradation and the loss of the parent protein bands on SDS/PAGE. Fragmentation can be inhibited by methionine and other agents (ascorbate, urate, Trolox C or GSH) capable of removing chloramines and reactive radicals. These results are consistent with protein-derived chloramines, and the radicals derived from them, as contributing agents in HOCl-induced plasma protein oxidation.
AB - Activated phagocyte cells generate hypochlorite (HOCl) via the release of H2O2 and the enzyme myeloperoxidase. Plasma proteins are major targets for HOCl, although little information is available about the mechanism(s) of oxidation. In this study the reaction of HOCl (at least 50 microM) with diluted fresh human plasma has been shown to generate material that oxidizes 5-thio-2-nitrobenzoic acid; these oxidants are believed to be chloramines formed from the reaction of HOCl with protein amine groups. Chloramines have also been detected with isolated plasma proteins treated with HOCl. In both cases chloramine formation accounts for approx. 20-30% of the added HOCl. These chloramines decompose in a time-dependent manner when incubated at 20 or 37 degrees C but not at 4 degrees C. Ascorbate and urate remove these chloramines in a time- and concentration-dependent manner, with the former being more efficient. The reaction of fresh diluted plasma with HOCl also gives rise to protein-derived nitrogen-centred radicals in a time- and HOCl-concentration-dependent manner; these have been detected by EPR spin trapping. Identical radicals have been detected with isolated HOCl-treated plasma proteins. Radical formation was inhibited by excess methionine, implicating protein-derived chloramines (probably from lysine side chains) as the radical source. Plasma protein fragmentation occurs in a time- and HOCl-concentration-dependent manner, as evidenced by the increased mobility of the EPR spin adducts, the detection of further radical species believed to be intermediates in protein degradation and the loss of the parent protein bands on SDS/PAGE. Fragmentation can be inhibited by methionine and other agents (ascorbate, urate, Trolox C or GSH) capable of removing chloramines and reactive radicals. These results are consistent with protein-derived chloramines, and the radicals derived from them, as contributing agents in HOCl-induced plasma protein oxidation.
KW - Adult
KW - Blood Proteins
KW - Chloramines
KW - Electron Spin Resonance Spectroscopy
KW - Female
KW - Free Radicals
KW - Humans
KW - Hypochlorous Acid
KW - Kinetics
KW - Male
KW - Nitrogen
KW - Oxidation-Reduction
KW - Temperature
M3 - Journal article
C2 - 10333500
VL - 340 ( Pt 2)
SP - 539
EP - 548
JO - Biochemical Journal
JF - Biochemical Journal
SN - 0264-6021
ER -
ID: 138282465