EPR spin-trapping of a myeloperoxidase protein radical.
Incubation of myeloperoxidase (MPO) with H(2)O(2) in the presence of the spin trap DBNBS (3,5-dibromo-4-nitrosobenzenesulfonic acid) results in the EPR-detectable formation of a partially immobilized protein radical. The radical was only formed in the presence of both MPO and H(2)O(2), indicating that catalytic turnover of the protein is required. The changes in the EPR spectrum of the adduct upon treatment with pronase confirm that the spin trap is bound to a protein residue. These results establish that MPO, like lactoperoxidase [Lardinois, O. M., Medzihradszky, K. F., and Ortiz de Montellano, P. R. (1999) J. Biol. Chem. 274, 35441-35448], reacts with H(2)O(2) to give a protein radical intermediate. The protein radical may have a catalytic role, may be related to covalent binding of the prosthetic heme group to the protein, or may reflect a process that leads to inactivation of the enzyme.
Lardinois
O M
OM
Department of Pharmaceutical Chemistry, School of Pharmacy, University of California, San Francisco, California 94143-0446, USA.
Ortiz de Montellano
P R
PR
D001557:Benzenesulfonates; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D006801:Humans; D008956:Models, Chemical; D009504:Neutrophils / Q000201:enzymology; D009603:Nitroso Compounds; D009195:Peroxidase / Q000737:chemistry / Q000378:metabolism*; D019097:Spin Trapping
D001557:Benzenesulfonates; D005609:Free Radicals; D009603:Nitroso Compounds; C048757:3,5-dibromo-4-nitrosobenzenesulfonate; D009195:Peroxidase