2,4,6-Trinitrotoluene reduction by carbon monoxide dehydrogenase from Clostridium thermoaceticum

Abstract

Purified CO dehydrogenase (CODH) from Clostridium thermoaceticum catalyzed the transformation of 2,4,6-trinitrotoluene (TNT). The intermediates and reduced products of TNT transformation were separated and appear to be identical to the compounds formed by C. acetobutylicum, namely, 2-hydroxylamino-4,6-dinitrotoluene (2HA46DNT), 4-hydroxylamino-2,6- dinitrotoluene (4HA26DNT), 2,4-dihydroxylamino-6-nitrotoluene (24DHANT), and the Barnberger rearrangement product of 2,4-dihydroxylamino-6-nitrotoluene. In the presence of saturating CO, CODH catalyzed the conversion of TNT to two monohydroxylamino derivatives (2HA46DNT and 4HA26DNT), with 4HA26DNT as the dominant isomer. These derivatives were then converted to 24DHANT, which slowly converted to the Barnberger rearrangement product. Apparent K(m) and k(cat) values of TNT reduction were 165 ± 43 μM for TNT and 400 ± 94 s-1, respectively. Cyanide, an inhibitor for the CO/CO2 oxidation/reduction activity of CODH, inhibited the TNT degradation activity of CODH.