Elected F.R.S. 1961
George Joseph Popják was a leading biochemist who introduced radioisotopic techniques to the study of metabolic pathways in the UK, and fully exploited their use in his own researches. His earlier work clarified the origin of triglycerides and cholesterol in the foetus as well as in milk, and paved the way for far-reaching discoveries in these fields. His group was the first to demonstrate that fatty acid biosynthesis occurs not in the mitochondria by the mere reversal of the β-oxidation pathway, but by a new cytosolic enzyme system. With J.W. Cornforth he dominated the field of cholesterol biosynthesis for nearly two decades. Their joint work reached new heights when they made intellectually cunning contributions to the mechanism and stereochemistry of several enzymic reactions involved between mevalonic acid and squalene. His later work was concerned with the understanding of the factors that, under physiological conditions, maintain cholesterol homeostasis and the development of novel strategies that can be used in the treatment of hypercholesterolaemia. Popják's early medical training and his great mastery of chemical enzymology provided a powerful combination for tackling biomedically important problems at a molecular level.