Is Hydrogen Tunneling Involved in AcylCoA Desaturase Reactions? The Case of a Delta(9) Desaturase That Transforms (E)-11-Tetradecenoic Acid into (Z,E)-9,11-Tetradecadienoic Acid This work was supported by Comisión Asesora de Investigación Científica y Técnica (grant AGF 98-0844), Comissionat per a Universitats i Recerca from the Generalitat de Catalunya (grant 97SGR-0021) and SEDQ S.A. We thank Prof. Nigel S. Scrutton (University of Leicester, UK) and Dr. Francisco J. Sanchez-Baeza (IIQAB, Barcelona, Spain) for helpful discussions, Dr. Josefina Casas and Dr. Antonio Delgado for critically reading the manuscript, and Germán Lázaro for rearing the insects used in this study. J.L.A. thanks the Spanish Ministry of Education and Science for a Postdoctoral Reincorporation Contract.