Several independent studies of bacterial degradation of nitrate ester explosives have demonstrated the
involvement of flavin-dependent oxidoreductases related to the old yellow enzyme (OYE) of yeast. Some of these
enzymes also transform the nitroaromatic explosive 2,4,6-trinitrotoluene (TNT). In this work, catalytic capabilities
of five members of the OYE family were compared, with a view to correlating structure and function.
The activity profiles of the five enzymes differed substantially; no one compound proved to be a good substrate
for all five enzymes. TNT is reduced, albeit slowly, by all five enzymes. The nature of the transformation
products differed, with three of the five enzymes yielding products indicative of reduction of the aromatic ring.
Our findings suggest two distinct pathways of TNT transformation, with the initial reduction of TNT being the
key point of difference between the enzymes. Characterization of an active site mutant of one of the enzymes suggests a structural basis for this difference.