Inhibition of cathepsins and related proteases by amino acid, peptide, and protein hydroperoxides

TY - JOUR

T1 - Inhibition of cathepsins and related proteases by amino acid, peptide, and protein hydroperoxides

AU - Headlam, Henrietta A

AU - Gracanin, Michelle

AU - Rodgers, Kenneth J

AU - Davies, Michael Jonathan

PY - 2006/5/1

Y1 - 2006/5/1

N2 - Reaction of radicals in the presence of O2, and singlet oxygen, with some amino acids, peptides, and proteins yields hydroperoxides. These species are key intermediates in chain reactions and protein damage. Previously we have shown that peptide and protein hydroperoxides react rapidly with thiols, and that this can result in inactivation of thiol-dependent enzymes. The major route for the cellular removal of damaged proteins is via catabolism mediated by proteosomal and lysosomal pathways; cysteine proteases (cathepsins) play a key role in the latter system. We hypothesized that inactivation of cysteine proteases by hydroperoxide-containing oxidised proteins may contribute to the accumulation of modified proteins within cells. We show here that thiol-dependent cathepsins, either isolated or in cell lysates, are rapidly and efficiently inactivated by amino acid, peptide, and protein hydroperoxides in a time- and concentration-dependent manner; this occurs with similar efficacy to equimolar H2O2. Inactivation involves reaction of the hydroperoxide with Cys residues as evidenced by thiol loss and formation of sulfenic acid intermediates. Structurally related, non-thiol-dependent cathepsins are less readily inactivated by these hydroperoxides. This inhibition, by oxidized proteins, of the system designed to remove modified proteins, may contribute to the accumulation of damaged proteins in cells subject to oxidative stress.

AB - Reaction of radicals in the presence of O2, and singlet oxygen, with some amino acids, peptides, and proteins yields hydroperoxides. These species are key intermediates in chain reactions and protein damage. Previously we have shown that peptide and protein hydroperoxides react rapidly with thiols, and that this can result in inactivation of thiol-dependent enzymes. The major route for the cellular removal of damaged proteins is via catabolism mediated by proteosomal and lysosomal pathways; cysteine proteases (cathepsins) play a key role in the latter system. We hypothesized that inactivation of cysteine proteases by hydroperoxide-containing oxidised proteins may contribute to the accumulation of modified proteins within cells. We show here that thiol-dependent cathepsins, either isolated or in cell lysates, are rapidly and efficiently inactivated by amino acid, peptide, and protein hydroperoxides in a time- and concentration-dependent manner; this occurs with similar efficacy to equimolar H2O2. Inactivation involves reaction of the hydroperoxide with Cys residues as evidenced by thiol loss and formation of sulfenic acid intermediates. Structurally related, non-thiol-dependent cathepsins are less readily inactivated by these hydroperoxides. This inhibition, by oxidized proteins, of the system designed to remove modified proteins, may contribute to the accumulation of damaged proteins in cells subject to oxidative stress.

KW - Amino Acids

KW - Animals

KW - Cathepsins

KW - Cell Line

KW - Free Radicals

KW - Hydrogen Peroxide

KW - Macrophages

KW - Mice

KW - Oxidation-Reduction

KW - Peptide Hydrolases

KW - Peptides

U2 - 10.1016/j.freeradbiomed.2005.12.036

DO - 10.1016/j.freeradbiomed.2005.12.036

M3 - Journal article

C2 - 16632114

SN - 0891-5849

VL - 40

SP - 1539

EP - 1548

JO - Free Radical Biology & Medicine

JF - Free Radical Biology & Medicine

IS - 9

ER -