Wednesday, November 05, 2008

Nobel Laureate: John Howard Northrop


The Nobel Prize in Chemistry 1946.

"for their preparation of enzymes and virus proteins in a pure form"

John Howard Northrop (1891 - 1987) was a renowned protein chemist who developed techniques for purifying and crystallizing enzymes.

He shared the prize with James Sumner, who first showed that proteins could be crystallized and with Wendell Stanley who crystallized tobacco mosaic virus.

Most biographers note that Northrop was very interested in genealogy and was proud to point out that he was a direct descendant of Joseph Northrop who settled in New Milford Connecticut in 1636 (John H. Northrop). I don't know if any other Nobel Laureates can trace their North American ancestors back 400 years.

The significanc of Northrops work is summarized in this excerpt from the presentation speech on the Nobel Prize website.

Nobel Laureates
Doctor John Northrop. You and your collaborators have developed the crystallization of enzymes and other active proteins into an art, of which you are the masters. The conditions for successful work in this field were explored by you, and in the course of that work interesting relationships between enzymes and related proteins were discovered, which may ultimately afford a clue to a fuller understanding of the mode of action of these substances.
We now know that trypsin, pepsin, and chymotrypsin are similar proteases that cleave other proteins. We also know that the active enzymes are derived from inactive precursors called zymogens. The zymogens (pepsinogen, trypsinogen, and chymtrypsinogen) are cleaved to remove part of the protein making the remainder into an acive enzyme. It's interesting to see how John H. Northrop described this discovery in his acceptance speech.
Formation of enzymes from their precursors. Pepsin, trypsin, and chymotrypsin are derived from inactive precursors. These precursors were isolated and crystallized and the formation of the active enzyme studied. The formation of pepsin from pepsinogen and trypsin from trypsinogen are autocatalytic reactions. These enzymes may therefore be "propagated", just as are bacteria. The formation of trypsin from trypsinogen may also be catalyzed by enterokinase, an enzyme of the digestive tract, or by an enzyme produced by a mold (Penicillium.) The formation of chymotrypsin from chymotrypsinogen is catalyzed only by trypsin, so far as is known. In all these reactions the increase in enzymatic activity is accompanied quantitatively by the appearance of the new enzyme protein which is quite different in all its properties from the original precursor. It seems to me that these results are perhaps the most convincing evidence that the enzymatic activity is actually a property of the protein molecule.

1 comment :

  1. I think that should be 1946.