The role of reactive N-bromo species and radical intermediates in hypobromous acid-induced protein oxidation

TY - JOUR

T1 - The role of reactive N-bromo species and radical intermediates in hypobromous acid-induced protein oxidation

AU - Hawkins, Clare Louise

AU - Davies, Michael Jonathan

PY - 2005/10/1

Y1 - 2005/10/1

N2 - Activated eosinophils, and hypobromous acid (HOBr) generated by these cells, have been implicated in the tissue injury in asthma, allergic reactions, and some infections. Proteins are major targets for this oxidant, but limited information is available on the mechanisms of damage and intermediates formed. Reaction of HOBr with proteins is shown to result in the formation of bromamines and bromamides, from side-chain and backbone amines and amides, and 3-bromo- and 3,5-dibromo-Tyr, from Tyr residues; these materials account for ca. 70% of the oxidant consumed. Protein carbonyls, dityrosine, and 3,4-dihydroxyphenylalanine are also formed, though these are minor products (<5% of HOBr added). With BSA, extensive (selective and nonspecific) protein fragmentation and limited aggregation are also observed. The bromamines/bromamides are unstable and induce further oxidation and free radical formation as detected by EPR spin trapping. Evidence was obtained for the generation of nitrogen-centered radicals on side-chain and backbone amide groups of amino acids, peptides, and proteins. These radicals readily undergo rearrangement reactions to give carbon-centered radicals. With proteins, alpha-carbon (backbone) radicals are detected, which may play a role in protein fragmentation. A novel damage transfer pathway from Gln side-chain amide groups to backbone sites was also observed.

AB - Activated eosinophils, and hypobromous acid (HOBr) generated by these cells, have been implicated in the tissue injury in asthma, allergic reactions, and some infections. Proteins are major targets for this oxidant, but limited information is available on the mechanisms of damage and intermediates formed. Reaction of HOBr with proteins is shown to result in the formation of bromamines and bromamides, from side-chain and backbone amines and amides, and 3-bromo- and 3,5-dibromo-Tyr, from Tyr residues; these materials account for ca. 70% of the oxidant consumed. Protein carbonyls, dityrosine, and 3,4-dihydroxyphenylalanine are also formed, though these are minor products (<5% of HOBr added). With BSA, extensive (selective and nonspecific) protein fragmentation and limited aggregation are also observed. The bromamines/bromamides are unstable and induce further oxidation and free radical formation as detected by EPR spin trapping. Evidence was obtained for the generation of nitrogen-centered radicals on side-chain and backbone amide groups of amino acids, peptides, and proteins. These radicals readily undergo rearrangement reactions to give carbon-centered radicals. With proteins, alpha-carbon (backbone) radicals are detected, which may play a role in protein fragmentation. A novel damage transfer pathway from Gln side-chain amide groups to backbone sites was also observed.

KW - Amides

KW - Bromates

KW - Bromides

KW - Cyclic N-Oxides

KW - Electron Spin Resonance Spectroscopy

KW - Electrophoresis, Polyacrylamide Gel

KW - Free Radicals

KW - Insulin

KW - Muramidase

KW - Oxidation-Reduction

KW - Protein Structure, Quaternary

KW - Proteins

KW - Ribonuclease, Pancreatic

KW - Serum Albumin, Bovine

KW - Spin Labels

KW - Trypsin Inhibitor, Kunitz Soybean

KW - Tyrosine

U2 - 10.1016/j.freeradbiomed.2005.05.011

DO - 10.1016/j.freeradbiomed.2005.05.011

M3 - Journal article

C2 - 16140210

SN - 0891-5849

VL - 39

SP - 900

EP - 912

JO - Free Radical Biology & Medicine

JF - Free Radical Biology & Medicine

IS - 7

ER -