Argentine biochemist who won the Nobel Prize for Chemistry in 1970 for his investigations of the processes by which carbohydrates (sugar) are converted into energy in the body.

After serving as an assistant at the Institute of Physiology, University of Buenos Aires, from 1934 to 1935, Leloir worked a year at the biochemical laboratory at the University of Cambridge and in 1937 returned to the Institute of Physiology, where he undertook investigations of the oxidation of fatty acids. In 1947 he obtained financial support to set up the Institute for Biochemical Research, Buenos Aires, where he began research on the formation and breakdown of lactose, or milk sugar, in the body. That work ultimately led to his discovery of sugar nucleotides, which are key elements in the processes by which sugars stored in the body are converted into energy. He also investigated the formation and utilization of glycogen and discovered certain liver enzymes that are involved in its synthesis from glucose.