THE NATURE OF ENZYME ACTION 305 



and hydrogen peroxide are formed. Now both these bodies are 

 poisonous and, if allowed to accumulate, the reaction would 

 soon come to an end. The formaldehyde is, however, rapidly 

 polymerised by the protoplasm of the chloroplast, and the 

 hydrogen peroxide is split up into oxygen and water by the 

 catalase. We see then why the reaction as a whole does not 

 occur in non-living preparations or extracts of green leaves. 

 Formaldehyde is, indeed, produced in the presence of chloro- 

 form on exposure to light, but since no polymerisation occurs 

 the chlorophyll is destroyed by it, and no further reaction is 

 possible. The production of hydrogen peroxide and formalde- 

 hyde even takes place in light in leaves killed by boiling, and in 

 this case, since the enzyme (catalase) is destroyed, as well as 

 the protoplasm, the hydrogen peroxide also contributes to the 

 destruction of the chlorophyll. 



Conclusion 



The living organism is enabled by the use of enzymes to bring 

 about, under ordinary conditions of temperature and moderate 

 concentrations of acid or alkali, many chemical reactions which 

 would otherwise necessitate high temperature or powerful 

 reagents. These enzymes are catalysts of a colloidal nature, 

 and obey the usual laws of catalytic phenomena. Certain 

 properties in which they differ from most inorganic catalysts are 

 to be explained by this colloidal condition. One such property 

 is destruction by heat and comparative instability as the tem- 

 perature rises, thus affording an explanation of the so-called 

 optimum temperature. The facility with which additive or 

 adsorption compounds are formed with substrate or products is 

 also due to the colloidal character of these enzymes. 



Literature 



Armstrong (E. Frankland), The Rate of the Change conditioned by Sucro- 

 clastic Enzymes, Proc. Roy. Soc. J2>i P- 5°°) 1904. 



The Influence of the Products of Change on the Rate of Change con- 

 ditioned by Sucroclastic Enzymes, Proc. Roy. Soc. 73, p. 516, 1904. 



Hydrolysis of Isomeric Glucosides, Proc. Roy. Soc. 74, p. 188, 1904. 



The Synthetic Action of Acids contrasted with that of Enzymes, Proc. 



Roy. Soc. B. 76, p. 592, 1905. 



Armstrong (H. E.), The Terminology of Hydrolysis, especially as affected 

 by Ferments, Chein. Soc. Trans. 1890, p. 528. Also footnote, Proc. Roy. Soc. 

 73, P- 5oo, 1904- 



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