394 ENZYMES * 



over 30 per cent of a pentose and an equimolecular propor- 

 tion of a hexose ; if it contains only two sugar molecules its 

 molecular weight ^would appear to be about 500 with three 

 atoms of nitrogen; it contains 5*5 per cent of ash, and 0*46 

 per cent of iron. Associated with it is an impurity, also 

 a introgenous glucoside, of higher molecular weight which 

 gives Millon's and xanthoproteic reactions ; it contains about 

 50 per cent of pentose, a hexose residue, and three atoms of 

 nitrogen to every two molecules of pentose. 



Preparation of Peroxidase. 



Appleman* recommends the following method of pre- 

 paring peroxidase. Potato tubers are grated into a pulp, 

 which is thoroughly mixed with calcium carbonate in order 

 to neutralize any acids. The mass is then ground with quartz 

 sand in a mortar for about two minutes and filtered through 

 butter muslin. The extract contains the peroxidase together 

 with oxidase ; the latter may be removed by raising the tem- 

 perature to 70 for ten minutes, whereby the oxidases are co- 

 agulated, or, according to Gruess,f any oxidase present may be 

 destroyed by adding acetone which does not affect the peroxi- 

 dase. In many experiments where only a dilute solution of 

 peroxidase is required I c.c. of extract to 300 c.c. of water 

 the heating may be dispensed with, as the amount of oxidase 

 is so very small. 



The method followed by Gruessl is somewhat different. 

 The potatoes are sliced into absolute alcohol, and the oxi- 

 dases destroyed by heating to 70 for ten minutes. The 

 slices are allowed to remain twenty-four hours in absolute 

 alcohol, which should be changed at least three times. The 

 material is then superficially dried with filter paper and 

 covered with ether for a few minutes. The dehydrated slices 

 are then freed from the alcohol and ether by placing in a 

 vacuum desiccator, after which they may be ground up in a 

 mortar. Before use, I gram of the powder is ground with 

 sand and 25 c.c. of water, and then filtered. 



This method is criticized by Appleman, who points out 

 that in the process of drying, the activity of the peroxidase is 



* Appleman : " Bot. Gaz.," IQII, 52, 306. 

 fGruess: "Ber. deut. hot. Gesells.," 1903, 21, 356. 

 JGruess: "Zeit. Pflanzenkrank," 1910, 25, 115. 



