428 SCIENCE PROGRESS 



importance in plant life is seen in the chlorophyll function ; 

 while it was noted by Reed (191 6) that in the ripening of pine- 

 apple fruit it increased, but the amount of oxidase remained 

 constant. 



Whatever, therefore, be the exact function of catalase in 

 the body, it obviously plays a large part in animal metabolism, 

 as it does in plants. It may not bring about the actual oxida- 

 tion, but there is increasing evidence that it is in some way 

 responsible for it. 



Reductase. — ^According to the more modern view, the power 

 of fresh animal and plant tissues to reduce nitrates to nitrites 

 is now explained by Bach's hydrolytic oxidative-reducing 

 reaction. Bach's view (191 3) is that the water of the system is 

 broken up so that an aldehyde is oxidised and hydrogen forms 

 a perhydride, which, through the influence of a perhydrase, 

 brings about the reduction. The so-called reductase is therefore 

 a perhydridase plus a perhydride which is formed from water 

 as a result of the action of an aldehyde. Of such a nature is 

 the reduction of milk by methylene blue. One observer, Woker, 

 had earlier put forward the suggestion that all oxidation enzymes 

 were merely different manifestations of an aldehyde, but this 

 claim is strongly refuted by Bach (191 5). 



Bach (191 3) showed the presence of a perhydridase in potato 

 juice, which in the presence of an aldehyde reduced nitrates. 

 He noted that the perhydridase utilised indifferently various 

 aldehydes. Apparently independently Abelous and Alloy 

 (19 1 8) confirmed somewhat the results of Bach. They de- 

 scribed a ferment present in milk and vegetable secretions which 

 can reduce nitrates and chlorates in the presence of an oxidisable 

 substance such as salicylaldehyde. This ferment, they found, 

 decomposed water, with the liberation of H- and OH- oin, and 

 then had a reducing and oxidising power. This ferment, which 

 they called an oxyhydrase, they suggested is a factor in the 

 antitoxic defence of the organism and is adapted to the 

 anaerobic life of the cells. 



AUeman (191 8) showed that the perhydrase apparently 

 followed the usual laws of enzyme action. He found that the 

 rate at which milk decolorised methylene blue was influenced 

 by the acidity of the milk which caused retardation, while the 

 disappearance of colour was hastened by temperature up to 

 55° C. and retarded at 75° C. 



Other Reactions. — ^Apart from the processes already stated 

 to be catalysed by enzymes, there are others in the animal and 

 vegetable world which apparently depend on enzymes. 



It has been shown that the chlorophyll in the leaves of 

 plants is associated with an enzyme which is active in alcoholic 

 solution. This enzyme — which is like a lipase or an esterase in 



