FULL PAPER Enzymes Antonio Bauzµ, David QuiÇonero, Pere M. Deyà, Antonio Frontera* &&&&—&&&& On the Importance of Anion–p Inter- actions in the Mechanism of Sulfide:- Quinone Oxidoreductase By a factor of FAD! Analysis of sulfi- de:quinone oxidoreductase (SQR; see picture) with and without the presence of flavin adenine dinucleotide (FAD) demonstrates the importance of anion– p interactions in the mechanism of action of sulfide oxidation. The nature of the addition–elimination mechanism has been analyzed and the barrier of the elimination step is reduced by the presence of the cofactor. Chem. Asian J. 2013, 00,0–0 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1 && These are not the final page numbers! ÞÞ FULL PAPER