TY - JOUR

T1 - Protein hydroperoxides and carbonyl groups generated by porphyrin-induced photo-oxidation of bovine serum albumin

AU - Silvester, J A

AU - Timmins, G S

AU - Davies, Michael Jonathan

N1 - Copyright 1998 Academic Press.

PY - 1998/2/15

Y1 - 1998/2/15

N2 - Porphyrin-sensitized photo-oxidation of bovine serum albumin results in oxidation at specific sites to produce protein radical species: at the Cys-34 residue (to give a thiyl radical) and at one or both tryptophan residues (Trp-134 and Trp-214) to give tertiary carbon-centered radicals and cause disruption of the indole ring system. This study shows that these photo-oxidation processes also consume oxygen and give rise to hydrogen peroxide, protein hydroperoxides, and carbonyl functions. The yield of hydrogen peroxide, protein hydroperoxides, and carbonyl functions is shown to be dependent on illumination time, the nature of the sensitizer, and the concentration of oxygen; the yield of hydroperoxides can also be markedly diminished by the presence of a spin trap which reacts with the initial protein radicals. The mechanism of formation of the protein hydroperoxides is suggested to be primarily through type I processes (i.e., independent of singlet oxygen), while type II (singlet oxygen) mechanisms may play a significant role in protein carbonyl formation. Reaction of the protein hydroperoxide species with metal ion complexes is shown to produce further protein-derived radicals which are predominantly present on amino acid side chains.

AB - Porphyrin-sensitized photo-oxidation of bovine serum albumin results in oxidation at specific sites to produce protein radical species: at the Cys-34 residue (to give a thiyl radical) and at one or both tryptophan residues (Trp-134 and Trp-214) to give tertiary carbon-centered radicals and cause disruption of the indole ring system. This study shows that these photo-oxidation processes also consume oxygen and give rise to hydrogen peroxide, protein hydroperoxides, and carbonyl functions. The yield of hydrogen peroxide, protein hydroperoxides, and carbonyl functions is shown to be dependent on illumination time, the nature of the sensitizer, and the concentration of oxygen; the yield of hydroperoxides can also be markedly diminished by the presence of a spin trap which reacts with the initial protein radicals. The mechanism of formation of the protein hydroperoxides is suggested to be primarily through type I processes (i.e., independent of singlet oxygen), while type II (singlet oxygen) mechanisms may play a significant role in protein carbonyl formation. Reaction of the protein hydroperoxide species with metal ion complexes is shown to produce further protein-derived radicals which are predominantly present on amino acid side chains.

KW - Animals

KW - Cysteine

KW - Electron Spin Resonance Spectroscopy

KW - Free Radicals

KW - Hydrogen Peroxide

KW - Light

KW - Oxidation-Reduction

KW - Oxygen

KW - Peroxides

KW - Photolysis

KW - Porphyrins

KW - Serum Albumin, Bovine

KW - Spin Trapping

KW - Tryptophan

U2 - 10.1006/abbi.1997.0495

DO - 10.1006/abbi.1997.0495

M3 - Journal article

C2 - 9473299

VL - 350

SP - 249

EP - 258

JO - Archives of Biochemistry and Biophysics

JF - Archives of Biochemistry and Biophysics

SN - 0003-9861

IS - 2

ER -