1913.] 



Studies on Enzyme Action. 



333 



strength and only about 4 per cent, when it was reduced to M/500 ; the 

 solution rapidly darkened in colour. As no action takes place in presence 

 of quinone (M/50), there can be little doubt that the effect produced by 

 quinol is dependent on the production of this compound directly ammonia 

 is present in sufficient amount to condition the oxidation of the quinol. 



A series of experiments were made with the monomethylic-derivative of 

 quinol, C 6 H 4 (OH) ■ OCH 3) a compound of some interest, as it is formed 

 together with quinol when arbutin is hydrolysed by emulsin. 



The material used was that supplied by Kahlbaum. "We were inclined 

 at first to attribute its inhibitive power to the presence of quinol ; we 

 therefore purified it by distilling it in vacuo and made use of the inter- 

 mediate fraction. The results given in Table B are those obtained with this 

 product. We then digested the compound with ferric chloride, with the 

 object of oxidising any quinol that might be present ; after treatment with 

 a little sulphite, to remove quinone, the residue was distilled in vacuo. As 

 the substance thus purified was as active as the original material, we are 

 inclined to think that in presence of ammonia and air monomethylated 

 quinol is slowly converted into quinone and that this is the reason why it 

 is so active an inhibitant (Graph 3). 



Glycine and Asparaginic — These substances accelerate the rate of change 

 as shown in Table A (Diagram 13). 



Though they are " neutral " compounds, they neutralise both acids and 

 bases ; their marked accelerative effect is probably due to the fact that 

 they serve to neutralise the ammonia as it is produced by the hydrolysis 

 of the urea. As the positive influence of glycine is no greater apparently 

 in more concentrated solutions, it is not improbable that it acts in two 

 directions, both serving to fix ammonia and combining also to some extent 

 with the enzyme. 



Carbonic Acid. — A further series of observations carried out in presence of 

 carbonic acid is given in Table C. The experiments were made in the manner 

 already described (XV, p. 121). The results are represented by graphs in 

 Diagram 15. 



The four graphs in Diagram 14 are drawn from data given in XV, Part L 

 They represent comparable results obtained in experiments carried out simul- 

 taneously with the same sample of enzyme. It will be noticed that whilst 

 the products of change taken together have but little influence, taken 

 singly they are relatively very active but in opposite directions. 



The set of graphs marked c (Diagram 15) show that when the proportion 

 of urea is varied the difference observed in the absence of carbonic acid 

 (XV, p. 117) is again apparent, the amount of change taking place in solutions 



' VOL. LXXXVI. — B. 2 B 



