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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 25, Number 5
BKCSDE 25(5)
May 20, 2004 

Peroxynitrite Inactivates Carbonic Anhydrase II by Releasing Active Site Zinc Ion
Young-Mi Kim, Sanghwa Han*
Carbonic anhydrase, Peroxynitrite, Inactivation, Zinc
Peroxynitrite enters erythrocytes through band 3 anion exchanger and oxidizes cytosolic proteins therein. As a protein associated with band 3, carbonic anhydrase II may suffer from peroxynitrite-induced oxidative damages. Esterase activity of carbonic anhydrase II decreased as the concentration of peroxynitrite increased. Neither hydrogen peroxide nor hypochlorite affected the enzyme activity. Inactivation of the enzyme was in parallel with the release of zinc ion, which is a component of the enzyme's active site. SDS-PAGE of peroxynitrite-treated samples showed no indication of fragmentation but non-denaturing PAGE exhibited new bands with lower positive charges. Western analysis demonstrated that nitration of tyrosine residues increased with the peroxynitrite concentration but the sites of nitration could not be determined. Instead MALDI-TOF analysis identified tryptophan-245 as a site of nitration. Such modification of tryptophan residues is responsible for the decrease in tryptophan fluorescence. These results demonstrate that peroxynitrite nitrates tyrosine and tryptophan residues of carbonic anhydrase II without causing fragmentation or dimerization. The peroxynitriteinduced inactivation of the enzyme is primarily due to the release of zinc ion in the enzyme's active site.
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