OBITUARIES

Meinhart H. Zenk

Meinhart Zenk, member and principal investigator at the Donald Danforth Plant Science Center, St. Louis, Missouri, and adjunct professor at the Department of Anesthesiology at Washington University, passed away after a long illness on July 5, 2011, at the age of 78. He was born in the small town of Donauwoerth on the Danube River in Southern Germany only a few days after the Machtergreifung of Adolf Hitler on January 30, 1933, and thus belonged to a generation that was just conscious enough at the time to carry the impressions of war (which had not left a male relative of his alive) and total collapse into adulthood.

Initially choosing chemistry as his major, Meinhart transferred to biology at the University of Munich, obtained a research assistantship at Purdue University, and returned in 1958 with a master of science in plant physiology. Only a year later, he was awarded his PhD with a thesis on indole-3-acetic acid activation and conjugation. After only another four years, he qualified for inauguration as an academic lecturer, in the Habilitation, a peculiarity of the academic system of German-speaking countries, now considered obsolete by many but defended by him up to his old age. His first series of publications were published either exclusively under his own name or together with one of his PhD students. He had no scientific father, mother, or mentor, did not come from a “school,” and was essentially a self-made scientist. He went his own way and followed his vision from the very start with pioneering work.

In his subsequent studies on the biosynthesis of various aromatic compounds in plants, such as benzoic and hydroxycinnamic acids, quinones, and so on, he developed supreme mastership in the chemical and enzymatic microsyntheses of radioactively labeled precursors and the purification and painstaking stepwise degradation of the labeled products for determination of the incorporation patterns. These were the heroic days before the advent of the use of stable isotopes, HPLC, immunoassays, GC- or LC-MS, NMR, and such in phytochemical and biosynthetic studies. But when these techniques became available, he always was among the first to adopt and exploit them to their full extent. While these talents won him the respect of the natural products chemists, his virtuosity in the identification, isolation, and characterization of enzymes of plant secondary metabolism, especially of those involved in the activation and stepwise reduction of lignin precursors, gave him early leadership in the rather tricky biochemistry of this metabolism.

In 1968, Meinhart became the first incumbent of the chair of plant physiology at the newly founded University of the Ruhr in Bochum and prominently contributed to its rising scientific reputation in the following dozen years or so. Here he began to explore the potential of plant cell cultures in the production of secondary compounds. While their industrial application would never meet the high expectations, Meinhart would later declare plant cell cultures “a pot of gold” in his chase of the enzymes of secondary metabolism. Cell cultures also turned out to be invaluable in the study of the regulation of secondary metabolism (by e.g., auxins, octadecanoid pathway intermediates, jasmonates). Now, starting a cell culture from some exotic species is more an art than a science, and it requires a great deal of experience and patience. Meinhart had carefully read the notable work Vom Kriege (On War, 1832) by Carl von Clausewitz, a Prussian military theorist, and he planned his scientific work farsightedly and meticulously like campaigns. Information would not leak until success was certain. Even to many in the Bochum group, it came as a surprise that his interest had turned to alkaloids. Meinhart’s entrée into the alkaloid field occurred with a bang, because the enzymatic studies had revealed beyond doubt that strictosidine, rather than vincoside (as believed by eminent researchers in the field), is the precursor of the indole alkaloids. A vast number of studies on alkaloid biosyntheses followed, too numerous to be cited here in detail. This work was now done at the University of Munich, where Meinhart held the chair of pharmaceutical biology from 1980 to 1999. It culminated in the painstaking identification of the 16 enzymes involved in the biosynthesis of morphine, the king of all drugs.

The Web of Knowledge chart of citations of Meinhart’s publications shows a highly respectable and steady number of 100–150 per year for the years 1968–1985; from then on a steep and steady increase to almost 700 per year in the first years of the new millennium can be seen, which brought Meinhart into the ISI list of Highly Cited Authors in Plant and Animal Sciences 1984–2004. Was this the scientific community’s fascination with alkaloid biosynthesis? No, it was the response to the almost serendipitous discovery of the phytochelatins, the heavy-metal-binding peptides, biosynthetically derived from glutathione, in plants, which was published in Science in 1985 and was followed by a series of articles that all stirred enormous interest. We see a confirmation here that the number of citations is not reliable as an indicator of the intellectual level or the originality of a publication, since Meinhart’s subsequent involvement in the elucidation of the enzymatic steps of the non-mevalonate pathway of terpenoid biosynthesis was in no way less exacting.

After retirement from Munich University and an interlude as honorary professor at the University of Halle–Wittenberg, Meinhart and his wife, Toni Kutchan, moved to St. Louis in 2006, where both assumed positions at the Donald Danforth Plant Science Center. Here, his last major contribution—and legacy—was the proof that mammals synthesize their own morphine from distant precursors. What will this discovery mean to pain research?

While none of Meinhart’s collaborators has been mentioned here by name, this must be so with Toni. It was she who brought the dimension of molecular biology to the Munich lab in the 1980s, who pursued a distinguished independent career in Halle and St. Louis, and who was a wonderful and much-loved companion to Meinhart.

Meinhart restlessly paced and paved the unending paths of plant secondary metabolism. This was the passion of his life. Even though he could sometimes offend people—friends not excepted—by prejudiced opinions and caustic remarks and letters, he was a highly sensitive man with an exquisitely developed sense of beauty in art, music, and lyrics. And there is so much beauty in his work!

Suffice it to say that Meinhart received numerous awards and distinctions for his work. For readers of the ASPB News, it may be of particular interest to know that the first of his three honorary doctoral degrees was awarded by Purdue University in 1991, that he was elected as foreign associate of the National Academy of Sciences in 1992 and as fellow of the American Society of Pharmacognosy in 2007, and that he was given the Phytochemical Pioneer Award of the Phytochemical Society of North America in 2010.

“Most of us are bricklayers. We are happy to add a stone to the edifice of science. . . . A rare few have the vision of an architect.” (Christian de Duve on Fritz Lipmann)

Meinhart was an architect.

Nikolaus Amrhein
Swiss Federal Institute of Technology, Zurich