Peroxidation of a specific tryptophan of metmyoglobin by hydrogen peroxide.

Globin-centered radicals at tyrosine and tryptophan residues and a peroxyl radical at an unknown location have been reported previously as products of the reaction of metmyoglobin with hydrogen peroxide. The peroxyl radical is shown here to be localized on tryptophan through the use of recombinant sperm whale myoglobin labeled with 13C at the indole ring C-3. Peroxyl radical formation was not prevented by site-directed mutations that replaced all three tyrosines, the distal histidine, or tryptophan 7 with non-oxidizable residues.

Reaction of myoglobin with hydrogen peroxide forms a peroxyl radical which oxidizes substrates.

Evidence is presented that the radical observed upon reaction of myoglobin with hydrogen peroxide is a peroxyl radical. Simulation of this spectrum gives principal values for the g tensor of gx = 2.0357, gy = 2.

Spectral analysis of the protein-derived tyrosyl radicals from prostaglandin H synthase.

We have analyzed the low temperature EPR spectra of the protein-derived tyrosyl radicals detected upon addition of arachidonic acid or 5-phenyl-4-pentenyl-1-hydroperoxide (PPHP) to prostaglandin H synthase. With either arachidonic acid or PPHP the initial radical detected is a doublet (peak-to-trough = 35 Gauss) that disappears rapidly and is replaced by a broad singlet (peak-to-trough = 30 Gauss) followed by a narrow singlet (peak-to-trough = 26.5 Gauss).

Free radical metabolism of halothane in vivo: radical adducts detected in bile.

Two radical adduct species have been detected in the bile of living rats treated with halothane and phenyl-N-t-butylnitrone (PBN). The treatment of rats with 12% oxygen was required for radical adduct detection. Analysis of the corresponding EPR spectra obtained when deuterated PBN and deuterated halothane or [2-13C]halothane was used shows that these two species result from the spin trapping of two halothane-derived free radicals.

Electron spin resonance investigation of tyrosyl radicals of prostaglandin H synthase. Relation to enzyme catalysis.

We have examined, by low temperature ESR, the protein-derived radicals formed by reaction of purified ram seminal vesicle prostaglandin H synthase (PHS). Upon addition of arachidonic acid or 5-phenyl-4-pentenyl-1-hydroperoxide (PPHP) to PHS reconstituted with Fe(III)-protoporphyrin IX (Fe-PHS) at -12 degrees C, an ESR spectrum was observed at -196 degrees C containing a doublet that rapidly converted into a singlet. These protein-derived radicals were identified as tyrosyl radicals.