Peroxynitrite scavenging by ferrous truncated hemoglobin GlbO from Mycobacterium leprae

Mycobacterium leprae GlbO has been proposed to represent merging of both O2 uptake/transport and scavenging of nitrogen reactive species. Peroxynitrite reacts with M. leprae GlbO(II)-NO leading to GlbO(III) via the GlbO(III)-NO species. The value of the second order rate constant for GlbO(III)-NO formation is >1 × 108 M−1 s−1 in the absence and presence of CO2 (1.2 × 10−3 M). The CO2-independent value of the first order rate constant for GlbO(III)-NO denitrosylation is (2.5 ± 0.4) × 101 s−1. Furthermore, peroxynitrite reacts with GlbO(II)-O2 leading to GlbO(III) via the GlbO(IV)O species. Values of the second order rate constant for GlbO(IV)O formation are (4.8 ± 0.5) × 104 and (6.3 ± 0.7) × 105 M−1 s−1 in the absence and presence of CO2 (=1.2 × 10−3 M), respectively. The value of the second order rate constant for the peroxynitrite-mediated GlbO(IV)O reduction (= (1.5 ± 0.2) × 104 M−1 s−1) is CO2-independent. These data argue for a role of GlbO in the defense of M. leprae against nitrosative stress.