Warburg, Otto Heinrich (1883–1970)

German biochemist who was awarded a Nobel Prize for Physiology or Medicine in 1931 for the discovery of respiratory enzymes that enable cells to process oxygen. In 1923 he devised a manometer (pressure gauge) sensitive enough to measure oxygen uptake of respiring tissue. By measuring the rate at which cells absorb oxygen under differing conditions, he was able to show that enzymes called cytochromes enable cells to process oxygen.

Later he discovered the mechanism of the conversion of light energy to chemical energy that occurs in photosynthesis. He also demonstrated that cancerous cells absorb less oxygen than normal cells.

Warburg was born in Freiburg im Breisgau and studied at Berlin and Heidelberg. In 1913 he went to the Kaiser Wilhelm (later Max Planck) Institute for Cell Physiology in Berlin, becoming a professor there in 1918 and its director in 1931. In 1941 Warburg, being part-Jewish, was removed from his post but such was his international prestige that he was soon reinstated. In 1944 he was nominated for a second Nobel Prize but Nazi rules prevented him from accepting the award.

Warburg discovered that in both charcoal systems and living cells, the uptake of oxygen is inhibited by the presence of cyanide or hydrogen sulphide, which combine with heavy metals.

He also showed that, in the dark, carbon monoxide inhibits the respiration of yeast but does not do so in the light. He was aware that heavy metals form complexes with carbon monoxide and that the iron complex is dissociated by light, which provided further evidence for the existence of an iron-containing respiratory enzyme. He then investigated the efficiency of light in overcoming the carbon monoxide inhibition of respiration, and determined the photochemical absorption spectrum of the respiratory enzyme, which proved to be a haemoprotein (a protein with an iron-containing group) similar to haemoglobin; he called it iron oxygenase.