PT  - JOURNAL ARTICLE
AU  - C Mottley
AU  - T B Trice
AU  - R P Mason
TI  - Direct detection of the sulfur trioxide radical anion during the horseradish peroxidase-hydrogen peroxide oxidation of sulfite (aqueous sulfur dioxide).
DP  - 1982 Nov 01
TA  - Molecular Pharmacology
PG  - 732--737
VI  - 22
IP  - 3
4099  - http://molpharm.aspetjournals.org/content/22/3/732.short
4100  - http://molpharm.aspetjournals.org/content/22/3/732.full
SO  - Mol Pharmacol1982 Nov 01; 22
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.