Krebs, Hans Adolf

Krebs, Hans Adolf

---

BRITISH BIOCHEMIST
1900–1981

Hans Krebs was born into a prosperous and well-educated family in Hildesheim, Germany. His father was a physician who specialized in otolaryngology, and it was Hans's intention to follow in his father's footsteps and become a physician. Krebs was educated at the Gymnasium Andreanum, and after World War I, he went on to study medicine at the Universities of Göttingen, Freiburg, and Berlin. In 1925 he earned an M.D. degree at the University of Hamburg. He was at this point passionately attracted to medical research, and he did not enter medical practice. In 1926, Krebs became an assistant to Professor Otto Warburg at the prestigious Kaiser Wilhelm Institute for Biology in Berlin, a post he held until 1930. Warburg (who later won the 1931 Nobel Prize in medicine) encouraged Krebs to pursue a career in research.

In 1931 Krebs moved to Freiburg to teach medicine. It was there that he authored (with Kurt Henseleit) his first important paper, which examined liver function in mammals and described how ammonia was converted to urea in liver cells. Krebs also studied the syntheses of uric acid and purines in birds. However, Krebs's research was cut short when the Nazis came to power in 1933. Krebs was Jewish, and he was therefore summarily fired from his post. He left Germany for England, taking a position at the School of Biochemistry at Cambridge University at the invitation of Sir Frederick Gowland Hopkins (who had won the 1929 Nobel Prize in medicine). In 1935 Krebs moved to the University of Sheffield to become a lecturer in pharmacology.

At Sheffield Krebs embarked upon the work that would elucidate some of the complex reactions of cell metabolism (the processes that extract energy from food). This extraction of energy is achieved via a series of chemical transformations that remove energy-rich electrons from molecules obtained from food. These electrons pass along a chain of molecular carriers in a way that ultimately gives rise to water and adenosine triphosphate (ATP) , which is the primary source of chemical energy that powers cellular activity.

Krebs found that the pivotal mechanism of cell metabolism was a cycle. The cycle starts with glycolysis, which produces acetyl coenzyme A (acetyl CoA) from food molecules—carbohydrates, fats, and certain amino acids. The acetyl CoA reacts with oxaloacetate to form citric acid. The citric acid then goes through seven reactions that reconvert it back to oxaloacetate, and the cycle repeats. There is a net gain of twelve molecules of ATP per cycle. Not only does this cycle (known as the Krebs cycle, and also as the tri-carboxylic acid cycle and the citric acid cycle) generate the chemical energy to run the cell, it is also a central component of the syntheses of other biomolecules.

Krebs published his groundbreaking paper on this cyclic component of cell metabolism in the journal Enzymologia in 1937, and it quickly became a foundational concept in biochemistry and cell biology. It was for this research that Krebs won the Nobel Prize in medicine in 1953. (He remains one of the most often cited scientists in cell biology, with his work being noted more than 11,000 times since 1961, when the citation records of original articles in cell biology began being counted.)

Krebs worked in both research and applied science in the area of cell metabolism and nutrition. During World War II he developed a bread that helped to keep the British people nourished at a time of food shortages. He developed new analytical techniques for research in cell biology and investigated other metabolic reactions, such as the synthesis of glutamic acid. He was also an energetic instructor. His students went on to become directors of laboratories and to win many prizes.

In 1954 Krebs was appointed the Whitley Chair of Biochemistry at Oxford University. That same year he received the Royal Medal of the Royal Society of London. In 1958, for his scientific work and his contributions to the lives of British people, Krebs was knighted. Even after his retirement in 1967, he continued to do research on liver disease, the genetic bases of metabolic diseases, and the link between poor nutrition and juvenile delinquency. In addition to his Nobel Prize and Royal Medal, he received honorary degrees from nine universities.

see also Glycolysis; Krebs Cycle.

Andrew Ede

Bibliography

Holmes, Frederic Lawrence (1991–1993). Hans Krebs, Vols. I and II. New York: Oxford University Press.

Krebs, Hans, and Johnson, W. A. (1937). "The Role of Citric Acid in Intermediate Metabolism in Animal Tissues." Enzymologia 4:148–156.

Krebs, Hans, and Martin, Anne (1981). Reminiscences and Reflections. Oxford, UK: Clarendon Press.

Internet Resources

More information available from <www.nobel.se/medicine/laureates/1953/>.