German-born Sir Hans Krebs, who spent the last 27 years of his life in Oxford, may not be well known outside scientific circles, but his pioneering research led to one of the most significant biochemical breakthroughs of the 20th century, and paved the way for further important discoveries about the workings of the mammalian body.

He was born Hans Adolf Krebs in Hildesheim on August 25, 1900, the middle of three children born to Dr Georg Krebs, a leading ear, nose and throat surgeon, and Alma Davidson, a banker’s daughter.

He was educated at the Gymnasium Andreanum and then served briefly in the army before embarking on medical studies at a number of different universities, including those at Götttingen, Freiburg-im-Breisgau, Munich and Berlin.

He became a medical interne at the Third Medical University Clinic in Berlin in 1924, and graduated a year later from the University of Hamburg.

His studies received a boost when, in 1926, he was appointed Research Assistant to Professor Otto Warburg, one of the foremost biochemists of the day, at the Kaiser Wilhelm Institute for Biology in Berlin-Dahlem. For the next four years, he gained valuable experience, learning the research techniques that laid the foundations for his future groundbreaking discoveries. Some years later, Krebs generously paid tribute to Warburg, crediting him as being his greatest single teacher, and his biography of Warburg was published by Oxford University Press in 1981.

In 1930 he returned to clinical work, first at the Municipal Hospital at Altona, under Professor L Lichtwitz, and then at the Medical Clinic at his old university at Freiburg-im-Breisgau, under Professor S Thannhauser.

The latter gave him greater opportunities for scientific investigation, and within a year he and an assistant, Kurt Henseleit, identified the chemical processes by which the liver converts ammonia into the less toxic urea (or uric acid) in animals. This was the first of the body’s metabolic cycles to be discovered, and led to medical advances in the recognition and treatment of liver disorders.

Krebs’ findings were published in 1932, and immediately hailed as a landmark discovery. The distinguished biochemist, Professor Hugh Blaschko, wrote that it “gave the answer to an important unsolved problem, that of the site and of the mechanism of urea biosynthesis in the mammalian body”, while Joseph S Fruton, of Yale University, commented that Krebs’ paper “marked a new stage in the development of biochemical thought”.

For Krebs, the publication of the paper resulted in an invitation from the English biochemist, Sir Frederick Gowland Hopkins, to work with him at the School of Biochemistry in Cambridge.

While Krebs was considering Hopkins’ invitation, fate lent a hand — the National Socialist German Worker’s Party came to power, and Krebs, as a Jew, was barred from practicing medicine in Germany.

His position at Freiburg was abruptly terminated, and in June 1933 he emigrated to England to take up Hopkins’ offer, escaping from Nazi-controlled Germany just before the situation for Jews became intolerable.

He worked with Hopkins for a year on a Rockefeller Studentship, after which he was appointed Demonstrator of Biochemistry at Cambridge University, a post he held for a further year.

In 1935, Krebs moved to Sheffield University to work as a Lecturer in Pharmacology. Three years later, he was appointed Lecturer-in-Charge at the newly-founded Department of Biochemistry.

This eventually led to a Professorship, and he also became Director of a Medical Research Council (MRC) research unit that was set up in his department. In 1937 he led another scientific breakthrough when he and a student, W.A. Johnson, discovered the citric acid cycle — now widely known as the Krebs Cycle — which plays an important part in the conversion of carbohydrates, fats and proteins in the body into usable energy. His paper was published that year in Enzymologia.

Acclaim for this discovery was a little slower coming — one journal, Nature, declined to publish the paper reporting his findings — and it was not until after the Second World War that he received proper recognition for this work.

He was duly rewarded, in 1947, by being elected a Fellow of the Royal Society of London, and in 1953 he was awarded half of the Nobel Prize in Physiology.

He came to Oxford a year later, when the MRC’s Unit for Research in Cell Metabolism was transferred to the University of Oxford. Krebs was appointed Whitley Professor of Biochemistry and became a Fellow of Trinity College, holding both posts for 13 years.

On his retirement in 1967, he became a research scientist at the Nuffield Department of Clinical Medicine, and was elected a Supernumerary Fellow of St Cross College. More significantly, he set up the Metabolic Research Laboratory at Radcliffe Infirmary, where he worked closely with colleagues such as L.V. Eggleston, R. Hems, Patricia Lund and D.H.Williamson. Krebs was granted British citizenship in 1939, a year after marrying Margaret Cicely Fieldhouse, of Wickersley, Yorkshire. The couple had a daughter, Helen, and two sons, Paul and John; the latter is currently Principal of Jesus College, Oxford.

By all accounts, Krebs was a likeable and approachable man, unaffected by his success and the widespread admiration he inspired. He was a popular and enthusiastic teacher, who was keen to pass on his skills and knowledge to the next generation of scientists.

The editor of Nature once commented that he was “a giant, eager that his shoulders should be used by younger people.” He was also known for the friendly atmosphere in his laboratories. Blaschko once commented that “he always created an air of cheerful activity around him”, while colleagues at Sheffield noted that the atmosphere was “one of unusual harmony as well as intellectual stimulation”.

He died at the Radcliffe Infirmary on November 22, 1981, after a short illness. The erection of a blue plaque in Iffley, more than 25 years after his death, joins the string of accolades awarded to him during his lifetime.