Professor Dr. Detlef Gröger receives the Egon Stahl Medal in Gold
05 January 2006 (online)
This year’s meeting of the Society for Medicinal Plant Research in Florence witnessed the bestowal of the Egon Stahl Medal in Gold on one of the grandseigneurs of pharmacognosy, Professor Dr. Detlef Gröger, who until his retirement was affiliated with the Institute of Biochemistry of Plants in Halle (later the Leibnitz Institut für Pflanzenbiochemie).
Professor Gröger was a disciple of Professor Kurt Mothes. He obtained his PhD in 1957 after submission of a thesis on ergot alkaloids. Early on two foci for his research in the ergot field crystallized. One was the isolation of Claviceps strains and the development of methods for the production of ergot alkaloids by fermentation in saprophytic culture. Starting with the fermentative production of alkaloids of the clavine type, which was systematically developed to submerged culture, during his sabbatical stay with V. E. Tyler in Seattle, Gröger became only the second scientist in the world to succeed in the production of the commercially important lysergic acid derivatives in culture, by fermentation of Paspalum ergot. The further development and optimisation of these fermentation procedures provided the tools for the extensive and definitive studies of the Gröger group on the biochemistry, enzymology and regulation of alkaloid formation in the ergot fungus.
The second focus of his ergot work became the biosynthetic pathway by which the ergot alkaloids are synthesized in the fungus. This work started with a series of seminal papers that demonstrated the biosynthetic origin of the ergoline ring system from tryptophan, mevalonic acid and a methyl group from methionine. This represented an entirely new paradigm, since plant physiologists had until then considered alkaloids and terpenoids to be mutually exclusive in the plant kingdom. It paved the way for the subsequent demonstration by several groups that the large family of plant indole alkaloids, e. g. the Vinca alkaloids, etc., is also of mixed terpenoid/amino acid origin.
Starting from this identification of the unexpected building blocks, Professor Gröger has over the course of this scientific life systematically unravelled the complicated biosynthetic pathway by which these alkaloids are assembled from their precursors. Beyond just demonstrating the transformations in intact cells, he often succeeded in isolating and characterizing the enzymes catalysing some of these reactions, a feat only appreciated by those who themselves have tried to isolate enzymes intact from these fungal cells loaded with proteases and nucleases. He also delineated the way in which the peptide moiety of the clinically used peptide ergot alkaloids is assembled from lysergic acid. He showed, importantly, that this does not involve ribosomal peptide bond formation and must thus occur on a non-ribosomal peptide synthase. On another front, he examined regulatory aspects of ergot alkaloid formation by studying the enzymology and physiology of formation of the alkaloid precursors.
Although the ergot alkaloids were clearly his favourites, they were by no means Professor Gröger’s only scientific interest. Rather, from early on he regularly tackled new problems in biosynthesis. Many of the compounds studied were higher plant alkaloids (e. g. harmanes, quinolozidines, indole alkaloids, acridones, benzylisoquinolines, spermidines, steroid alkaloids), others were non-alkaloidal natural products, such as anthraquinones or ß-lactams. For the study of alkaloid biosynthesis in plants, cell culture techniques were developed for the target plants, to provide more suitable experimental systems for biochemical studies. Important contributions were made by the Gröger group to our understanding of the biosynthesis of many of these compounds, but most prominently for the acridone alkaloids. These compounds were shown to be formed from anthranilic acid by a ”polyketide” biosynthesis, a process analogous to flavonoid biosynthesis. The biochemical investigation of this biosynthesis led to the isolation of the responsible polyketide synthase enzyme and culminated in the cloning and expression of the gene encoding this acridone synthase. This crowning achievement is reported in Professor Gröger’s last scientific publication.
Professor Gröger’s life work contributed an impressive body of scientific knowledge to its field. His contributions were novel, timely and often pioneering. In judging these accomplishments, one must also consider the difficult circumstances under which the work was done. During much of his scientific life the DDR tried to isolate its scientists from the western world by restricting travel and communication, the shortage of foreign currency constantly disrupted access to scientific materials and equipment, and political pressure forced individuals who wanted to maintain their personal integrity to make difficult choices (it was learned after the fall of the Berlin Wall that a key co-worker of Professor Gröger was a Stasi informer and that the Stasi had tried to prevent Professor Gröger’s children from being admitted to university). Despite these pressures and under considerable personal risk, Professor Gröger kept up contacts and collaborations with colleagues throughout the world in order to maintain as much as possible the competitiveness of his research program. Thus, he deserves recognition not only for the volume and importance of his scientific work, but also for his scientific and personal courage and integrity.
We offer him our heartiest congratulations and best wishes for future health and happiness.
H. G. Floss, Seattle, USA
E. Leistner, Bonn, Germany
R. Bauer, Graz, Austria, President of GA Fig.