RT Journal Article
SR Electronic
T1 Direct detection of the sulfur trioxide radical anion during the horseradish peroxidase-hydrogen peroxide oxidation of sulfite (aqueous sulfur dioxide).
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 732
OP 737
VO 22
IS 3
A1 C Mottley
A1 T B Trice
A1 R P Mason
YR 1982
UL http://molpharm.aspetjournals.org/content/22/3/732.abstract
AB The ESR spectrum of SO3- is observed directly during the oxidation of (bi)sulfite to sulfate by horseradish peroxidase. This radical exhibits a single line at g = 2.0031. The SO3-radical can be trapped with nitrosobenzene, yielding an ESR spectrum with coupling constants AN = 12.3 G,AHp = AHo = 2.4 G, and AHm = 0.9 G, and a g-value of 2.0053. SO3- is an intermediate in the two-step reduction of peroxidase Compound I by (bi)sulfite at physiological pH. At low pH, no SO3- is observed, which indicates a direct, one-step, two-electron reduction of Compound I. The pH at which the mechanism changes depends on the isoenzymes present. The radical reacts rapidly with oxygen as evidenced by the absence of an ESR spectrum when oxygen is present and by oxygen uptake measurements.