Elsevier

Redox Biology

Volume 23, May 2019, 101115
Redox Biology

Research Paper
2-Alkenal modification of hemoglobin: Identification of a novel hemoglobin-specific alkanoic acid-histidine adduct

https://doi.org/10.1016/j.redox.2019.101115Get rights and content
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Highlights

  • 2-Alkenal-treated hemoglobin was subjected to a comprehensive analysis of the modified histidine.

  • The alkanoic acid-type histidine adducts were identified as novel adducts formed in the 2-alkenal-modified hemoglobin.

  • This type of adducts was suggested to be formed by the iron-dependent oxidation of 2-alkenal-histidine Michael adducts.

  • The alkanoic acid-type histidine adducts were generated in red blood cells exposed to H2O2.

Abstract

α,β-Unsaturated aldehydes generated during lipid peroxidation, such as 2-alkenals, give rise to protein degeneration in a variety of pathological states. 2-Alkenals are highly reactive toward nucleophilic amino acid residues, such as histidine and lysine, to form Schiff base adducts or Michael addition adducts. In this study, upon the reaction of hemoglobin with 2-octenal, we unexpectedly detected a product corresponding to the reduced form of the 2-octenal-histidine Michael adduct plus 14 mass unit. Based on the LC-ESI-MS/MS analysis of synthetic adduct candidates, the adduct was identified to be Nτ-(1-carboxyheptan-2-yl)-histidine (CHH), a novel alkanoic acid-type histidine adduct. The alkanoic acid-histidine adducts were detected in the 2-alkenal-treated hemoglobin and myoglobin, but not in the 2-alkenal-treated cytochrome c and transferrin. The addition of hemin to the reaction mixture, containing a non-heme protein and 2-alkenals, resulted in the formation of the alkanoic acid-histidine adducts, suggesting that a heme iron may play a role in the oxidation of covalently modified proteins. Moreover, using the stable isotope dilution method, we showed evidence for the endogenous formation of CHH in red blood cells exposed to hydrogen peroxide. Thus, this study establishes a novel mechanism for covalent modification of proteins by 2-alkenals, in which heme iron is involved in the formation of the alkanoic acid-histidine adducts. The potential implications of this novel adduct are discussed.

Keywords

Lipid peroxidation
Aldehyde
Hemoglobin
Protein chemical modification
Red blood cells

Abbreviations

LC-ESI-MS/MS
liquid chromatography with electrospray ionization tandem mass spectrometry
PUFA
polyunsaturated fatty acids
HSA
human serum albumin
PP IX
protoporphyrin IX
RBCs
red blood cells
SRM
Selected reaction monitoring
m/z
mass-to-charge ratio
CHH
Nτ-(1-carboxyheptan-2-yl)-histidine
LDL
low-density lipoproteins

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