We analyze the coupled electron-proton transfer from the NfsA nitroreductase enzyme to the trinitrotoluene (TNT) explosive as a possible reaction mechanism for nitrocompounds sensing. Based on earlier experiments, we have chosen as active site a group of amino acids around the flavin mononucleotide cofactor. In this site, we evaluate charge transfer, leading to a first step in the enzymatic TNT degradation that is enough for its detection. Our analysis suggests that light absorption and vibrations around the active site induce charge transfer for the enzymatic reaction with TNT.© 2010 IEEE.