This volume contains the lectures and discussions of the 34th Mosbach Colloquium, organized by the Gesellschaft fur Biologische Chemie in commemoration of otto Warburg's 100th anniversary. Following warburg's main scientific interests the topics of the contributions were related to the hydrogen-transferring enzymes as well as to the oxygen-reducing and oxygen-activating enzymes. Due to the detailed knowledge on the molecular structure of NAD- and flavin-dependent dehydrogenases, a better understanding of enzyme catalysis and especially enzyme evolu- tion has emerged. In the field of oxidases...