HARDEN , SIR ARTHUR

Harden was born in Manchester and educated at Owens College there (where he subsequently taught) and at the University of Erlangen, Germany. He was professor of biochemistry at the Jenner (later Lister) Institute of Preventive Medicine, where he began research into alcoholic fermentation, continuing the work of Eduard Buchner who had discovered that such reactions can take place in the absence of living cells.

Harden demonstrated that the activity of yeast enzymes was lost following dialysis (the separation of large from small molecules by diffusion of the smaller molecules through a semipermeable membrane). He went on to show that the small molecules are necessary for the successful action of the yeast enzyme and that, whereas the activity of the large molecules was lost on boiling, the activity of the small molecules remained after boiling. This suggested that the large molecules were proteins but the small molecules were probably nonprotein. This was the first evidence for the existence of coenzymes – nonprotein molecules that are essential for the activity of enzymes. Harden also discovered that yeast enzymes are not broken down and lost with time, but that the gradual loss of activity with time can be reversed by the addition of phosphates. He found that sugar phosphates are formed during fermentation as intermediates – phosphates are now known to play a vital part in biochemical reactions. Knighted in 1936, Harden shared the 1929 Nobel Prize for chemistry with Hans von Euler-Chelpin for his work on alcoholic fermentation and enzymes.