SELMAN A. WAKSMAN 277 



Zymases are produced in abundance by a number of bacteria, especially those 

 forming lactic and acetic acids. The reductases produced by bacteria have been 

 studied extensively in connection with the Schardinger reaction or the reduction of 

 dyes in milk. Among the oxidases' which are produced by bacteria, it is sufficient 

 to mention tyrosinase, luciferase, and various phenolases. 



Catalase is produced abundantly by various aerobic bacteria as well as by bacteri- 

 al spores, the time of maximum formation of the enzyme depending upon the nature 

 of the organism and composition of medium. Anaerobic bacteria produce practically 

 no catalase; this accounts for the sensitiveness of these organisms to H2O2 and to 

 oxygen. A definite relation was found' to exist between the reducing power of bac- 

 teria and their capacity for forming peroxide, anaerobes tending to produce peroxide 

 in the presence of oxygen. The formation or presence of catalase prevents the accumu- 

 lation of the peroxide and injury to the growth of the bacteria. Hence the ability of 

 an organism to produce catalase may account for its ability to grow in an atmosphere 

 containing free oxygen.^ 



IMPORTANCE OF ENZYMES IN LIFE-PROCESSES 



Most of the nutrients which are available to bacteria, both in artificial culture 

 media and under natural conditions, are not in a form that can be utiHzed by these 

 organisms for metabolic purposes. These nutrients must first undergo a series of 

 changes, which are largely brought about by means of enzymes produced by the 

 bacterial cells. These changes include the processes of decomposition, which result 

 in the transformation of the complex organic substances into simpler compounds, and 

 the processes of oxidation which lead to the liberation of large quantities of energy. 

 In addition to these changes, which result in the degradation of the complex organic 

 substances, the synthesizing activities of the cell (as well as most processes of reduc- 

 tion) are also carried out by means of enzymes. The simpler substances formed from 

 the complex organic materials by processes of hydrolysis, oxidation, and reduction 

 are utiHzed as building stones for the synthesis of bacterial protoplasm and other 

 complex organic materials. 



Since bacteria vary in the nature of the nutrients which they can utilize and in 

 the conditions under which these nutrients are utilized, the nature of the enzymes 

 produced by the different organisms will also vary. 



The enzymes do not increase the energy content of the system nor do they influ- 

 ence the equilibrium conditions. However, they do influence the rapidity with which 

 the equilibrium is reached or the time required to carry out a certain process. 



GENERAL REFERENCES 



Bayliss, W. M.: The Nature of Enzyme Action. 5th ed. London, 1925. 

 Euler, H. V.: Chemie der Enzyme. Part I. 3d ed. 1925; Part II, Abt. i and 2. 2d ed. 

 Munchen. 1922-27. 



' F"elton, L. D.: J. Exper. Med.. 38, 291. 1923; /. Inject. Dls., 34, 407. 1924. 



^ M'Leod, J. M., and Gordon, J.: J. Path. &° Bad., 26, 326, 332. 1923; 38, 147, 155. 1923. 



^ See chap, xiv in this volume. 



