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 and oxygenases we begin to understand the complex biochemistry of oxygen and realize that binding, reduction, and activation of this molecule have common underlying prin- ciples. Even new metabolic pathways of oxygenases, such as lipoxygen- ases or cyclooxygenase, have recently been discovered and promise new innovations in cell regulation and medicine. Thanks to the cooperation of all authors, a well-balanced mixture of basic information and progress report was provided. We especially ap- preciate Professor Bucher's charming, thoughtful, and honest contri- bution on Otto Warburg as a skilful scientist and colorful personality. The editors are indebted to the sponsoring organizations, the Deutsche Forschungsgemeinschaft and several industrial companies, and especial- ly acknowledge the competent help of Mrs. H. Allen in the editorial work. H. SUND October 1983 V. ULLRICH Contents Otto Warburg: A Personal Recollection Th. BUcher (With 15 Figures) **. . *****. **********. . ****. . ******** NAD-Dependent Dehydrogenases structure-Function Relationships of NAD-Dependent Dehydrogenases M. G.