Glutamine is a key aminoacid for the synthesis of numerous biologic- ally important compounds in mammalian cells and is a carrier form of ammonia. The advance in knowledge on the metabolic significance of this amino acid is presented in in-depth treatments by experts in this active research field. This includes the enzymology of glutamine synthe- tase and glutaminase activities in different mammalian organs, notably liver, kidney and brain; properties of glutamine transport across bio- logical membranes; role of glutamine metabolism in the liver, with emphasis on the recent discovery of intercellular heterogeneity with respect to enzyme distribution and its functional consequences for ammonia/urea metabolism and pH regulation; renal and intestinal glutamine metabolism; cerebral glutamine/ glutamate interrelationships; skeletal muscle; role of glutamine in cell culture; and finally the clinical aspects, including the new outlook of glutamine antagonists in cancer therapy as well as the role of glutamine in hepatic coma and encephalo- pathy. Some, but not all, of the contributors to this work attended the 48th Conference of the Gesellschaft fur Biologische Chemie on glutamine metabolism held in Gottingen, W. Germany, in September 1983. This conference was supported by the Stiftung Volkswagenwerk, Dr. H. Falk Foundation, Freiburg, and the J. Pfrimmer Co. , Erlangen. The abstracts of the contributions to the conference were published in Hoppe-Seyler's Z. Physiol. Chem. 364,1237-125,6,1983, and this book is not intended as the proceedings of that meeting.

The serene phrase, Lest I forget thee, glutathione ..., coined by the Kosowers (1) to describe the state in the 1960's, must be replaced now by something like "Inevitable GSH" in order to characterize the current situation. The surge in interest on the ubiquitous tripeptide has been ama- zing, with publications on GSH running at rates as high as one per day, so that it seemed appropriate to convene international experts for a discussion of recent develop- ments this year. Unlike the two previous meetings in this decade held in Tlibingen in 1973 (2) and in santa Ynez in 1975 (3), the scope was restricted to Functions of Gluta- thione in Liver and Kidney. Only in this way did an in-depth discussion of the current state of knowledge in a limit- ed topic appear possible. The last couple of years have seen a fascinating pro- ductivity in the fields of (a) Regulation of the Glutathione Level in the Liver, (b) Role of y-Glutamyltransferase in Gluta- thione Turnover with emphasis on the renal enzyme, and a critical appraisal of the y-Glutamyl Cycle, (c) Hyd:roperox- ide and Disulfide Metaholism, enriched by the discovery of the nonseleniurn-dependent glutathione peroxidase activ- ity and its relation to the glutathione-S-transferases, and the participation of the 2GSH/GSSG system in redox transitions in intact organ, cells and isolated mito- chondria, and (d) a multitude of Pharmacological and Toxi- cological Aspects related to glutathione, mainly centered on the events leading to liver damage and the protective

The scope of the 20th Mosbach Colloquium may be best illustrated by the following notes sent to the speakers when the colloquium was organized. "1) The application of inhibitors in cell biology has led to decisive insight into the organisation of cellular units. The subject should be treated against a background of current aspects of cell biology. In some areas of research, a fairly complete picture of the functions and cooperative interactions of the units has already emerged. We will discuss mainly these areas. 2) At this colloquium we want to contribute illustrations of the useful application of inhibitors to biological problems. Due to limited knowledge, inhibitors are sometimes incorrectly employed. This applies both to the planning of investigations and to the con* clusions drawn ("use of inhibitors by uninhibited workers"). 3) Inhibitors themselves are interesting substances and their mechanisms of action constitute fascinating problems." The colloquium has been subdivided into five sections. The known chemical structures of the inhibitors discussed are given in an Appendix. We gratefully appreciate the cooperation of the speakers. To a great extent, they managed the coordination of contributions to each of the five subdivisions. We regret that no contributors from Eastern Europe were able to participate.