Effects of iodide on the fluorescence and activity of the hydroperoxyflavin intermediate of Vibrio harveyi luciferase.

The 4a-hydroperoxy-4a,5-dihydroFMN intermediate (II or HFOOH) of Vibrio harveyi luciferase is known to transform from a low quantum yield IIx to a high quantum yield (lambdamax 485 nm, uncorrected) IIy fluorescent species on exposure to excitation light. Similar results were observed with II prepared from the alphaH44A luciferase mutant, which is very weak in bioluminescence activity. Because of the rapid decay of the alphaH44A II, its true fluorescence was obscured by the more intense 520 nm fluorescence (uncorrected) from its decay product oxidized flavin mononucleotide (FMN).

2,4,6-trinitrotoluene reduction by an Fe-only hydrogenase in Clostridium acetobutylicum.

The role of hydrogenase on the reduction of 2,4,6-trinitrotoluene (TNT) in Clostridium acetobutylicum was evaluated. An Fe-only hydrogenase was isolated and identified by using TNT reduction activity as the selection basis. The formation of hydroxylamino intermediates by the purified enzyme corresponded to expected products for this reaction, and saturation kinetics were determined with a K(m) of 152 micro M.