A cDNA encoding a newly identified isotype of peroxiredoxin (Prx) was isolated from a Chinese cabbage flower bud cDNA library and designatedCPrxII.Database searches using the predicted CPrxII amino acid sequence revealed no substantial homology to other proteins with the exception of the yeast type II Prx with which CPrxII shares 27.8% sequence identity. Recombinant CPrxII expressed inEscherichia coliwas able to protect glutamine synthetase from inactivation in a metal-catalyzed oxidation system and to reduce H 2 O 2 with electrons provided by thioredoxin. This specific antioxidant activity of CPrxII was about 6-fold higher than that of 2Cys-Prx of the same plant. In contrast to 2Cys-Prx, which is predominantly expressed in leaf tissue of cabbage seedlings,CPrxIIis highly expressed in root tissue as revealed by Northern and Western blot analyses. TheCPrxIIgene exists as a small multigene family in the cabbage genome.