484 ENZYMES 



a negative result does not necessarily indicate the absence of 

 these enzymes. 



Deans * prepared peptidase from the seeds of beans by ex- 

 tracting the cotyledons with water, filtering, and half saturating 

 the filtrate with ammonium sulphate. The precipitate thus 

 obtained is filtered off, dissolved in water and separated from 

 ammonium sulphate by dialysis. The solution of enzyme thus 

 purified may be dried at a temperature below 50° C. 



Vines f separated protease from peptidase by making use of 

 the fact that the former is hardly soluble in water but readily 

 so in a dilute solution of sodium chloride, whilst peptidase is 

 easily soluble in water. The material, e.g. seed of Cannabis 

 saliva, is ground and extracted with a lO per cent solution of 

 sodium chloride. The solution is filtered and rendered just 

 acid by the addition of acetic acid, whereby a white precipitate 

 of protein is formed, which is filtered off. The acid filtrate 

 has marked proteolytic qualities but has no action on fibrin ; 

 it therefore contains the peptidase. The fibrin-digesting pro- 

 tease is in the precipitate ; to recover it, wash the precipitate 

 with a 10 per cent solution of sodium chloride slightly acidified 

 with acetic acid. The precipitate is next treated with distilled 

 water and filtered ; the filtrate, which has an opalescent appear- 

 ance, digests fibrin but has no effect on Witte peptone. In 

 order to ensure the best results, the temperature should be 

 kept as low as possible during filtration. 



Grover and Chibnall % prepared the enzyme (asparagin- 

 ase) responsible for the deamidation of asparagine from the 

 young roots of germinated barley as follows : after 8-9 days 

 germination, the seedhngs were dried in an incubator at 37° C. 

 for three days. By vigorous shaking the dried roots were 

 broken from the grain and were separated by sifting through a 

 coarse sieve ; 200 grams of root were ground with 1-5-2 litres 

 of water for two hours and the liquor pressed out in a Buchner 

 press. The residue was ground for another hour with 1-5 

 litres of water and again pressed. The combined extracts 

 were centrifuged and the clear hquid precipitated with 4-5 



* Deans : " Bot. Gaz.," 1905, 39, 321. 



t Vines : " Ann. Bot.," 1908, 22, 103. XLoc. cit. 



