NADH peroxidase activity of rubrerythrin

P. S. Alban et al. (J. Appl. Microbiol. (1998) 85, 875- 882) reported that a mutant H2O2-resistant strain of Spirullum (S.) volutans showed constituti ve overexpression of a protein whose amino acid sequence and molecular weig ht closely resembled that of a subunit of rubrerythrin, a non-heme iron pro tein with no known function. They also reported that the mutant strain, but not the wild-type, showed NADH peroxidase activity. Here we demonstrate th at rubrerythrin and nigerythrin from Desulfovibrio vulgaris and rubrerythri n from Clostridium perfringens show NADH peroxidase activities in an in vit ro system containing NADH, hydrogen peroxide, and a bacterial NADH oxidored uctase. The peroxidase specific activities of the rubrerythrins with the "c lassical" heme peroxidase substrate, o-dianisidine, are many orders of magn itude lower than that of horseradish peroxidase. These results are consiste nt with the phenotype of the H2O2-resistant strain of S. volutans. The reac tion of reduced (i.e., all-ferrous) rubrerythrin with excess O-2 takes seve ral minutes, whereas the anaerobic reaction of reduced rubrerythrin with hy drogen peroxide is on the millisecond time scale and results in full oxidat ion of all iron centers to their ferric states. Rubrerythrins could, thus, function as the terminal components of NADH peroxidases in air-sensitive ba cteria and archaea. (C) 1999 Academic Press.