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Summary Article: Theorell, Axel H(ugo) T(heodor) (1903–1982) from The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide

Swedish biochemist who was awarded the Nobel Prize for Physiology or Medicine in 1955 for his discoveries concerning the nature and mode of action of oxidation enzymes.

Theorell advanced the field of enzyme research by developing the techniques required to isolate enzymes and study their reaction mechanisms. His first breakthough came in the 1930s when he isolated a pure sample of the enzyme, known only as the ‘old yellow’ enzyme from yeast. He successfully split the enzyme and proved that it was made up from the coenzyme, yellow riboflavin (vitamin B2) phosphate and a protein component. In 1934 he showed that this coenzyme was instrumental in the oxidation of glucose and that the mechanism for the reaction involved the binding of a hydrogen atom at a specific site in the riboflavin molecule. This was the first time in which enzyme activity had been linked to a specific atom. Theorell went on to study the role of iron atoms present in many oxidative enzymes and produced significant research on peroxidases, which had not been possible prior to Theorell's techniques due to the speed of their reactions. He also established the function of the cytochrome group of enzymes and showed that they acted as a source of oxygen, which was accessed when the oxygen content of the blood was depleted. Theorell's work considerably advanced the study of enzyme research and led to a better understanding of how enzymes function.

Theorell was born in Linköping, Sweden. He received his MD degree from the Karolinska Institute, Stockholm, in 1930, where he was appointed lecturer in physiological chemistry. Theorell was appointed associate professor at the Uppsala University in 1932. He held a Rockefeller fellowship from 1933 until 1935 and studied at the Kaiser Wilhelm Institute, Berlin-Dahlem, Germany. He was director of the Nobel Medical Institute, Stockholm, from 1937 until 1970.

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