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Northrop, John Howard

enzymes protein pure crystalline

(1891–1987) US biochemist: obtained a range of crystalline enzymes.

Educated at Columbia University, New York, Northrop worked throughout his career at the Rockefeller Institute in the same city, starting in 1916. In 1926 J B Sumner (1877–1955) had for the first time crystallized an enzyme (a biochemical catalyst) and showed it to be a protein. (Remarkably, he was a skilled bench chemist, despite losing his left arm in a gun-shot accident in his teens.) However, the value of this work, on the enzyme urease, was insufficiently grasped by most researchers. Northrop saw its importance and used similar methods to obtain pure crystalline samples of other enzymes; he did this in the early 1930s. His pure enzymes included the digestive enzymes trypsin and pepsin, and also ribonuclease and deoxyribonuclease. They were found to be proteins (as, in fact, all enzymes appear to be). This work changed both attitudes and techniques; enzymes were no longer regarded as mysterious, and the availability of pure enzymes was of great value in laboratory work. Later, in 1938, Northrop isolated a bacterial virus and showed this also to be a type of protein (a nucleo-protein). He shared the 1946 Nobel Prize for chemistry with Sumner and , who had first crystallized a plant virus.

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