OXIDASES OR OXIDISING ENZYMES. 267 



ioo° C. If, however, after cooling - , there is added to the 

 extract a little of the precipitate yielded when the juice 

 of fresh grapes is treated with a large excess of alco- 

 hol, it regains the power. There is thus present in the 

 grapes themselves, as in the wine prepared from them, 

 a certain amount of this oxidising substance which from its 

 behaviour must be classed with laccase and tyrosinase as 

 an oxidising enzyme. 



The name cenoxydase has been given to this body. It 

 appears to resemble laccase very closely, but it is not certain 

 that it is identical with it. 



Martinand has ascertained it to be present in other 

 fruits than grapes ; plums, pears and apples especially may 

 be mentioned. It appears to develop with the ripening of 

 the fruit, unripe grapes containing very little. A good deal 

 seems to be lost in the preliminary process of wine-making, 

 wine itself containing relatively little when compared with 

 the freshly expressed grape juice. 



Martinand (21) finds that the cenoxydase can be removed 

 from wine by shaking it with ether, which takes from it a 

 body having some of the properties of tannin ; this becomes 

 olive-green or yellowish-brown on the addition of ferric 

 chloride, is turned red by alkalies, and gives a white pre- 

 cipitate with albumin but not with gelatin. After the wine 

 has undergone oxidation, most samples do not give up this 

 body to ether, and many others yield only very small 

 quantities of it. 



Wine treated with ether in this way, and kept neutral, 

 is not subject to self-oxidation. 



The enzyme is possibly, associated in the wine, there- 

 fore, with this body which is soluble in ether. 



Martinand (20) finds that the oxidase is destroyed when 

 its solution is heated to 72 and kept at that temperature 

 for four minutes. Exposure to 55 C. for i| hours is also 

 fatal to it. Intermediate temperatures bring about the same 

 destruction after intermediate times of exposure. 



Bouffard (22) has observed that the temperature of 

 destruction varies a good deal under different circumstances. 

 He has found that wines beginning to be attacked with 



