(1883–1970) German physiologist
Warburg, who was born at Freiburg im Breisgau in Germany, was the son of Emil Warburg, a distinguished professor of physics at Berlin. Otto was educated at the University of Berlin, where he obtained his PhD in 1906, and at Heidelberg, where he gained his MD in 1911. He joined the Kaiser Wilhelm Institute for Biology in 1913, attaining professorial status in 1918, and in 1931 became director of the Kaiser Wilhelm Institute for Cell Physiology, renamed after Max Planck following World War II. Here Warburg remained in charge until his death at the age of 86.
When the human body converts lactic acid into carbon dioxide and water it consumes oxygen. In the early 1920s Warburg began to investigate just how such aerobic metabolism works. To do this he designed, in 1923, the Warburg manometer, which is used to measure the rate of oxygen uptake by human tissue. It was clear to Warburg that such a reaction could only take place at normal temperatures with the aid of enzymes but, because of the tiny amounts involved, such enzymes would be impossible to isolate by orthodox analytical techniques. He suspected the respiratory enzymes to be the cytochromes discovered a decade earlier and consequently set out to explore their nature by noting which substances affected the rate of oxygen uptake. He first noted that intercellular respiration was blocked by hydrogen cyanide and by carbon monoxide. This suggested to Warburg that the respiratory enzymes contained iron on the analogy that carbon monoxide acts on hemoglobin by breaking the oxygen–iron bonds. Support for such a supposition was derived from the similarity between the spectrum of the carbon monoxide–hemoglobin complex and that of the carbon monoxide–respiratory enzyme complex.
Warburg also studied the metabolism of cancerous cells and in 1923 discovered that malignant cells use far less oxygen than normal cells and can in fact live anaerobically. This extremely interesting observation led him to speculate that cancer is caused by a malfunction of the cellular respiratory system. He advocated that cancer might be prevented by avoiding foods and additives that impair cellular activity and by ensuring a high level of respiratory enzyme in the body by taking plenty of iron and vitamin B.
Warburg also worked on other enzyme systems, particularly the flavoproteins, or yellow enzymes, active in cellular dehydrogenation. He found that the coenzyme flavin adenine dinucleotide (FAD) is the active part of flavoproteins and later demonstrated that nicotinamide is similarly the active part of nicotinamide adenine dinucleotide (NAD+). Following these discoveries he showed that in alcohol fermentation a hydrogenated form of NAD+ (NADH2) reacts with acetaldehyde to give NAD+ and ethyl alcohol.
For his contributions to biochemistry, Warburg was nominated three times for the Nobel Prize for physiology or medicine, in 1926, 1931, and 1944, although he only actually received the award in 1931.
Subjects: Science and Mathematics.