358 Messrs. R J. Caldwell and S. L. Courtauld. [May 9, 



or that one and the same enzyme (amygdalase) is concerned in the hydro- 

 lysis of both amygdalin and methyl-a-glucoside.* 



It is noteworthy that after the maltase is destroyed there is a coincident 

 variation in the amount of amygdalin and methyl-a-glucoside which undergo 

 hydrolysis in the case of different yeasts (Tables IY and V). 



Moreover, a yeast extract in which the maltase has been destroyed 

 produces an effect on a mixture of methyl-a-glucoside and amygdalin markedly 

 smaller than the sum of its effects on the two compounds taken separately 

 (Table VIII). As there is competition for the enzyme when two substances 

 are hydrolysed together (cf. Henri),f this result would also seem to show that 

 a single enzyme is active. 



It has been stated by Ter MeulenJ that only glucose retards the hydro- 

 lysis of amygdalin by emulsin and that maltose is without effect. Apparently 

 maltose is without effect on the hydrolysis of amygdalin by amygdalase 

 (Table VIII) ; and in this respect galactose and lactose are also inert, whilst 

 glucose has a marked inhibitory effect. 



It is impossible at present to identify amygdalase with any known enzyme. 

 The enzyme is present in varying amounts in the different yeasts we have 

 examined, and appears to be equally well extracted from the dried material 

 at all temperatures from 15° to 45°. Whereas a low temperature of extrac- 

 tion, 0°, affords a very small proportion of active amygdalase (Table III), 

 the quantity is increased by heating the extract for a short time at 45° ; a 

 similar effect is produced by heating an extract prepared at 15° (Table IV) : 

 that is to say, the amygdalase is originally dissolved as part of a more 

 complex protein or zymogen molecule, which is hydrolysed at the higher 

 temperatures. Proof of its stability is afforded by the fact that it is con- 

 tained in invertase prepared by O'Sullivan and Thompson's method, which 

 involves the autolysis of the yeast and precipitation of the enzj^me by 

 alcohol — a process which entirely destroys maltase. 



* Marino and Sericano speak of using 20 kilogrammes of yeast. After this had been 

 washed and dried, it was extracted with water ; the precipitate produced by adding 

 alcohol to the extract was purified by dialysis. Eventually they obtained only 2*5 grammes 

 of dried substance. They state definitely that their invertase was prepared by continuing 

 the dialysis until methyl-a-glucoside was no longer affected. However, they give no 

 details of the experiments which proved this to be the case and it is noteworthy that 

 amygdalin appears to have been but slowly hydrolysed by their material, even when this 

 was used in large proportion. 



t ' C. E. Soc. Biol.,' 1903, vol. 55, p. 868. 



X < Eec. Trav. Chim.,' 1905, vol. 24, p. 444. 



