Enzymes: Machine Tools of the 

 Cellular Factory^ 



By B. A. KiLBY 



Department of Biochemistry, The School of Medicine, University of Leeds, England 



[With 1 plate] 



The first half of the present century has seen biochemistry develop 

 from a humble servant of physiology into a master science in its own 

 right. Its vast field of study is the chemistry of all forms of life, from 

 the simplest bacteria to the higher plants and animals, and in this 

 study it calls upon the services of almost every other branch of science. 

 Much attention has been paid to the elucidation of the structure of 

 the compounds which make up the living cell, and in recent years an 

 increasing emphasis has been placed on studying how the cell func- 

 tions. Much is known of the nature of the raw material entering the 

 factory of the cell and of the products made there, and now the interest 

 has switched to finding out more about the intricate machinery and 

 processes which take place inside the factory. The machine tools of 

 the cell are its enzymes or ferments which enable it to carry out the 

 remarkable range of chemical reactions that make life possible. 



There was a very vigorous discussion during the nineteenth century 

 concerning the nature of fermentation. Why, it was asked, did 

 insipid grape juice turn apparently spontaneously into wine — why did 

 wort change into beer ? What was the nature of the scum or sediment, 

 the yeast, which appeared at the same time ? In France, a prize equal 

 in value to a kilogram of gold was offered in 1800 for the best answer 

 to the question "What distinguishes substances which act as ferments 

 from the materials they are capable of fermenting?" Although the 

 prize was never awarded, its offer did much to stimulate discussion 

 and controversy, as yeast was considered at that time to be a chemical 

 byproduct of fermentation, and it was widely believed that it played 

 no essential part in the process. 



About 1837, three workers claimed independently to have shown 

 that yeast was a living organism and was responsible for fermenta- 



' Reprinted by permission from Discovery, March 1951. 



273 



