H sub(2)O sub(2) and super(?)NO scavenging by Mycobacterium leprae truncated hemoglobin O

Kinetics of ferric Mycobacterium leprae truncated hemoglobin O (trHbO?Fe(III)) oxidation by H sub(2)O sub(2) and of trHbO?Fe(IV)?O reduction by super(?)NO and NO sub(2) super(-) are reported. The value of the second-order rate constant for H sub(2)O sub(2)-mediated oxidation of trHbO?Fe(III) is 2.4x10 super(3)M super(-) super(1)s super(-) super(1). The value of the second-order rate constant for super(?)NO-mediated reduction of trHbO?Fe(IV)?O is 7.8x10 super(6)M super(-) super(1)s super(-) super(1). The value of the first-order rate constant for trHbO?Fe(III)?ONO decay to the resting form trHbO?Fe(III) is 2.1x10 super(1)s super(-) super(1). The value of the second-order rate constant for NO sub(2) super(-)-mediated reduction of trHbO?Fe(IV)?O is 3.1x10 super(3)M super(-) super(1)s super(-) super(1). As a whole, trHbO?Fe(IV)?O, generated upon reaction with H sub(2)O sub(2), catalyzes super(?)NO reduction to NO sub(2) super(-). In turn, super(?)NO and NO sub(2) super(-) act as antioxidants of trHbO?Fe(IV)?O, which could be responsible for the oxidative damage of the mycobacterium. Therefore, Mycobacterium leprae trHbO could be involved in both H sub(2)O sub(2) and super(?)NO scavenging, protecting from nitrosative and oxidative stress, and sustaining mycobacterial respiration.