(b. Hamburg, Germany, 10 November 1874; d. Frankfurt, Germany, 25 July 1933)
Embden, son of a Hamburg lawyer, studied medicine at the universities of Freiburg im Breisgau, Munich, Berlin, and Strasbourg. His teachers, Johannes von Vries in Freiburg and Franz Hofmeister in Strasbourg, directed his interest toward physiology. In 1903 Embden was appointed assistant at the Physiological Institute, having worked in Hofmeister’s laboratory since his graduation in 1899. He also worked for short periods with Gaule in Zurich, Paul Ehrlich in Frankfurt, and Ernst Ewald in Strasbourg. These brief stints increased Embden’s skill in experimentation. But it was Hofmeister’s influence that was decisive in directing him toward chemicophysiological research and in increasing his ability to think in a biologically oriented way.
In 1904 Carl von Noorden made Embden director of the newly organized chemistry laboratory of the medical clinic at the municipal hospital of Frankfurt-Sachsenhausen. Embden helped to create such a fine reputation for this laboratory that in 1907 it was expanded into the Physiological Institute. In 1909 this institute became autonomous, and in 1914, with the founding of the university, it was renamed the University Institute for Vegetative Physiology, with Embden as director and full professor. In 1907 Embden had qualified as lecturer at the University of Bonn on the basis of his work in Frankfurt. Two years later he was appointed professor. He married Hanni Fellner, granddaughter of Frankfurt’s former lord mayor. From 1925 to 1926 he served as rector of the university.
In his lectures, as in his research, Embden preferred a presentation of the deeper relationships of chemicophysiological processes to a collection of individual facts. At the Physiological Institute he created an atmosphere of dedicated teamwork through his sympathy, helpfulness, and ability to foster close personal contacts and inspire his assistants to cooperate in the solution of common problems. Embden was known as a researcher who made absolutely sure of his results, without impeding his bold conclusions and theories.
At the time Embden began his biochemical research, the physiology of metabolism was still dominated by the energy principle, and pertinent research was concentrated mainly on the initial and final stages of the metabolic processes. Embden focused on the biologically specialized position of the chemical processes in the living organism and particularly investigated the several stages of intermediate metabolism. His works form an important part of the transition from calorimetric investigations to the physiology of the metabolism of the living cell. Embden’s scientific works are divided into two large, clearly distinct, and logically related groups. Initially he investigated intermediate metabolic processes in the liver in order to consider the physiological-chemical processes involved in muscular exertion.
Embden recognized that experiments on the undissected animal produced unclear results, while dissected tissue was unsatisfactory because of breakdown of the organic structure and cell damage. Therefore he developed a new method by using the livers of warm-blooded animals, kept in good condition by a special perfusion technique. With the help of this method he recognized oxidative deamination as a way to break down amino acids, the synthesis of sugar from lactic acid, and—in connection with the β-oxidation of fatty acids discovered by Franz Knoop— that acetoacetic acid and acetone are the products of pathological sugar metabolism. This last discovery formed a basis for research into sugar metabolism and diabetes. In their entirety, these investigations showed that the liver is the most important metabolic-physiological organ of the body.
Embden’s research work on intermediate carbohydrate metabolism turned his attention to the chemical processes involved in muscular activity. At first he selected the fluid pressed from a muscle—analogous to fluid pressed from yeast—as a cell-free research medium. In 1924 he succeeded in isolating a hexose diphosphate as an intermediate product, naming it lactacidogen. It showed him that—analogous to the processes in the yeast cell—glucose must be esterified with phosphoric acid before it can be broken down further. In 1927 he discovered hexose monophosphate, the so-called “Embden ester,” in the muscle cells. During twenty years of tenacious work Embden and his assistants isolated important phosphor-containing intermediate products of carbohydrate metabolism in the muscle. This led to his discovery of adenyl phosphoric acid in the muscle, thus opening a new, large field in biochemistry. Embden was the first to recognize the rapid reversibility of chemical processes in muscle contraction. Finally, in the course of his last experiments, in 1932–1933, he and his assistants succeeded in tracing all stages of the breakdown of glycogen in the muscle to lactic acid. In these biochemical investigations Embden never lost sight of the problem of general cell physiology, always endeavoring to integrate his discoveries of phosphorylation and metabolic processes with the relationships between activity, fatigue, and training on the one hand and the colloidal state of protoplasm on the other.
I. Original Works. Embden’s inaugural dissertation is Anatomische Untersuchung eines Falles von Elephantiasis fibromatosa (Strasbourg, 1899). Posthumously there appeared “Gustav Embdens und seiner Mitarbeiter letzte Arbeiten,” in Hoppe-Seyler’s Zeitschrift für physiologische Chemie, 230 (1934), 1–108, with a biography (not by Embden).
II. Secondary Literature. On Embden or his work see H. J. Denticke, “Gustav Embden,” in Ergebnisse der Physiologie (biologischen Chemie und experimentellen Pharmakologie), 35 (1933), 32–49, with a bibliography; E. Lehnartz, “Gustav Embden,” in Arbeitsphysiologie, 7, no.5 (1934), 475 483; and J. C. Poggendorff, VI, pt. 1, 660; VIIa, pt. 1, 500.