Bicarbonate enhances the hydroxylation, nitration, and peroxidation reactions catalyzed by copper, zinc superoxide dismutase. Intermediacy of carbonate anion radical. J Biol Chem 2000 May 12;275(19):14038-45
Date
05/09/2000Pubmed ID
10799477DOI
10.1074/jbc.275.19.14038Scopus ID
2-s2.0-0034640515 (requires institutional sign-in at Scopus site) 108 CitationsAbstract
The effect of bicarbonate anion (HCO(3)(-)) on the peroxidase activity of copper, zinc superoxide dismutase (SOD1) was investigated using three structurally different probes: 5, 5'-dimethyl-1-pyrroline N-oxide (DMPO), tyrosine, and 2, 2'-azino-bis-[3-ethylbenzothiazoline]-6-sulfonic acid (ABTS). Results indicate that HCO(3)(-) enhanced SOD/H(2)O(2)-dependent (i) hydroxylation of DMPO to DMPO-OH as measured by electron spin resonance, (ii) oxidation and nitration of tyrosine to dityrosine, nitrotyrosine, and nitrodityrosine as measured by high pressure liquid chromatography, and (iii) oxidation of ABTS to the ABTS cation radical as measured by UV-visible spectroscopy. Using oxygen-17-labeled water, it was determined that the oxygen atom present in the DMPO-OH adduct originated from H(2)O and not from H(2)O(2). This result proves that neither free hydroxyl radical nor enzyme-bound hydroxyl radical was involved in the hydroxylation of DMPO. We postulate that HCO(3)(-) enhances SOD1 peroxidase activity via formation of a putative carbonate radical anion. This new and different perspective on HCO(3)(-)-mediated oxidative reactions of SOD1 may help us understand the free radical mechanism of SOD1 and related mutants linked to amyotrophic lateral sclerosis.
Author List
Zhang H, Joseph J, Felix C, Kalyanaraman BAuthor
Balaraman Kalyanaraman PhD Professor in the Biophysics department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AnimalsAnions
Bicarbonates
Catalysis
Cations
Cattle
Cyclic N-Oxides
Free Radicals
Hydrogen Peroxide
Hydroxylation
Nitrates
Spin Labels
Superoxide Dismutase
Tyrosine
