180 



SCIENCE. 



[N. S. Vol. XX. No. 501. 



Concerning the specific action of a few vege- 

 table ferments, sucli as diastase, invertase and 

 lipase, a fairly clear and definite idea has been 

 formed, but as regards the functions of other 

 enzymes, particularly those of oxidizing and 

 reducing properties, our knowledge is much 

 less precise, and the greatest diversity of opin- 

 ion prevails. 



As an example of the confusion which ex- 

 ists it is only necessary to review what has 

 been written within the past few years re- 

 garding catalase. The property which ex- 

 tracts from animal and vegetable tissues pos- 

 sess of decomposing hydrogen peroxide was 

 observed by Schoenbein in 1863, but Loew* 

 was the first to ascribe the reaction to a spe- 

 cific enzyme — catalase — to which he attributed 

 both oxidizing and reducing properties. Loew 

 is of the opinion that, in the respiration proc- 

 esses of the living cell, hydrogen peroxide is 

 formed and that this compound would act 

 detrimentally were it not for the fact that it 

 is destroyed immediately by the catalase. A 

 similar view is shared by Pozzi-Escot,t who, 

 however, declares that catalase is a reducing 

 enzyme and has no oxidizing properties. 

 Kastle:^ and Loevenhart, on the other hand, 

 believe that catalase is concerned purely with 

 oxidatipn phenomena and that Loew's sugges- 

 tion, that it prevents the accumulation of 

 hydrogen peroxide, is highly improbable. 

 Without desiring to controvert any of the 

 above opinions, I would like to suggest an- 

 other possible explanation as to the role of the 

 oxidizing and reducing enzymes. 



In the course of experiments with sugar 

 cane I have frequently observed that cane, 

 which had been sterilized by steaming, suffers 

 a more rapid deterioration through the attack 

 of molds and bacteria than raw cane. This 

 also holds true, but less noticeably, of the 

 juices from steamed and raw cane. Another 

 observation frequently made was that the 

 juice from the upper green portion of a living 



*Loew, U. S. Dept. Agr. Report No. 68. 

 ' Catalase, a New Enzyme of General Occurrence.' 



■|- Pozzi-Escot, American Chemical Joxirnal, 

 June, 1903, p. 552. 



J Kastle and Loevenhart, American Chemical 

 Journal, June, 1903, p. 583. 



cane was more resistant towards fermentation 

 than juice from the riper joints lower down. 

 The juice from the top of the cane also under- 

 went a very rapid darkening after pressing, 

 while that from the middle and bottom ex- 

 hibited this change to a much less degree. 

 The juice from steamed cane undergoes no 

 coloration whatever. The change in color, 

 resulting from the exposure of the juice or 

 tissues of the cane to the air, is much better 

 observed if the stalk be divided lengthwise; 

 the darkening begins almost instantly in the 

 region of the apex or growing point, and is 

 less and less marked towards the bottom of 

 the stalk. Such coloration phenomena are 

 common to the tissues and juices of most 

 plants and, according to Bertrand, are to be 

 explained by the action of an oxidizing en- 

 zyme upon bodies of a tannin nature. Such 

 bodies occur in fact in the sugar cane, and 

 microchemic tests show them to be most 

 abundant in the growing parts. 



From the association of coloration phe- 

 nomena with resistance to fermentation, it is 

 natural to conclude that the dark-colored oxi- 

 dation products produced by enzymes may 

 have a toxic or germicidal action. That 

 germicidal products, of even a very pro- 

 nounced character, may be formed in cane 

 juice by enzyme action was shown as follows: 

 Samples of raw and sterilized juice from ripe 

 cane were treated respectively with 0.2 per 

 cent, of resorcin, orcin, pyrogallol and hydro- 

 quinone, and left exposed to the air. In every 

 instance the sterilized juices began to ferment 

 first; as regards the raw juices, thosei treated 

 with resorcin and orcin showed the least re- 

 sistance to fermentation and those treated 

 with pyrogallol and hydroquinone the greatest. 

 The raw juice treated with hydroquinone 

 turned nearly black in color and remained 

 perfectly preserved for many weeks. In this 

 case the toxic agent was no doubt quinone, 

 the presence of which was plainly indicated 

 by the odor. In the oxidation processes which 

 take place, through enzyme action, when the 

 tissues of green plants are cut or bruised, a 

 quinone body may be formed, or, perhaps, an 

 organic peroxide of the asymmetric peracid 



