1901] 



Studies on Enzyme Action. 



515 



sugar and that of diastase by maltose than is that of lactase, emulsin 

 or maltase by the products to which they respectively give rise. 

 Consequently, for these latter enzymes, the linear period is of short 

 duration (Tables II, IV, VII, XI) and the logarithmic period is barely 

 perceptible, owing to the rapid reduction in the rate. 



Case IV. — When the amount of enzyme and water is kept constant 

 whilst that of sugar is increased, it may be supposed that the 

 magnitude of the active system will increase until s-t-e reaches a 

 maximum, a definite equilibrium being established between enzyme, 

 sugar, and water, the whole of the enzyme, perhaps, becoming com- 

 bined with the sugar. It may be assumed that if the amount of 

 sugar be further increased, the equilibrium will remain unaffected, 

 notwithstanding that an addition of sugar is practically equivalent to 

 a withdrawal of water. 



But if s + e remain unaltered, whatever the proportion of sugar 

 present beyond a certain minimum, a constant amount of hydrolyte 

 will undergo change in a given time, although the proportion changed 

 as also the value of K will decrease as the concentration is increased. 

 This conclusion is entirely in agreement with the facts elucidated, 

 especially by Adrian Brown, and with my own observations. 



Lastly, it should be pointed out that in discussing the action of 

 enzymes, besides taking into account the conditions affecting the 

 formation of an active system and the part which such a system plays 

 in hydrolysis, it is necessary to consider the relative stability or 

 tendency to break down under the influence^of water of the combina- 

 tion of enzyme and sugar in connection with the very different rates 

 at which different enzymes condition hydrolysis. Generally speaking, 

 the observed differences in the rate at which hydrolysis is effected may 

 be conditioned by — 



(a) Specific differences in the enzymes, e.g., lactase as compared 

 with emulsin, which both hydrolyse milk sugar. 



(b) Differences in the configuration of the hydrolyte, e.g., /3-methyl 

 glucoside and /3-methyl galactoside, which are both hydrolysed by 

 emulsin. 



(c) Differences in the stability of the hydrolytes, e.g., cane sugar as 

 compared with milk sugar. 



But it is very difficult to institute just comparisons, for whereas, 

 in the case of acids, the effect of only a single substance on the variety 

 of sugars may be contrasted, in studying the hydrolysis of sugars 

 under the influence of enzymes, it is necessary in most cases to use a 

 different enzyme for each sugar, so that positive data are not easily 

 obtained. Experiments made under comparable conditions with acids 

 to test their action on different sugars show that these are hydrolysed 

 at very different rates : thus, for instance, whilst cane sugar is 

 hydrolysed nearly 1000 times as rapidly as maltose, this latter under- 



VOL. LXXIII. 2 



