ON THE HYDROLYSIS OF SUGARS. ^89 



It has been from time to tuue pointed out by varioua observers that 

 the relative strengths of the acids depend on the sugar by means of which 

 the comparison is made, and even with the same sugar the ratio is 

 different at different temperatures ; it is difficult to see how these facts 

 can be reconciled with the hydrogen ion theory of sugar catalysis. 



N. — The Analogy between Acid and En:.ytae CaUdyniis. 



It was emphasised by Omeis that, altliougli the effect of tempera- 



1889 ^^^^ ^^ different in the two cases, yet there is no essential diflerence 



between enzyme and acid catalysis. Ostwald has more recently 



1901 ^'^^'^^^ ^^'^^y ' ^-''^ action of enzymes is entirely analogous to that of 



catalysts in general.' 



Granting that the analogy exists, it is necessary to consider whether 

 we ought to modify our opinion of the manner in which either acid or 

 enzyme act in order to bring the two cases into agreement. 



With regard to the action of enzyme, even Euler has not attempted to 

 apply an ionic explanation ; on the other hand, there is no parallel among 

 the numerous theories of acid catalysis for the enzyme radiation theory o^f 

 Barendrecht. ' The only hypothesis which is equally applicable to the two 

 cases is the addition theory. In the case of enzymes the e\-idence is 

 strongly in favour of this view ; but in the case of acids, as the foregoing 

 pages will have demonstrated, the issue is not so simple. 



The ' active system ' theory, as Dr. E. F. Armstrong and the author 

 have shown, is not at variance with any of the known facts of catalysis 

 by acids, whilst the alternative ionic explanation is beset with difficulties. 



They have stated that the difference in behaviour of acids and enzymes 

 respectively as hydrolytic agents 'is due mainly if not Avholly (1) to the 

 superior affinity of the enzymes for the carbohydrates, (2) to the very 

 different behaviour of the two classes of hydrolysts towards water, which 

 is a consequence of the crystalloid nature of the one and the colloid 

 nature of the other.' The amount of water present appears to have very 

 little influence on the activity of an enzyme, whilst in the case of acids it 

 is a ^■ery important determining factor in the rate. 



On the other hand, the enormous activity of a few molecules of en- 

 zyme, compared with that of the strongest acids, is to be attributed to the 

 above-mentioned causes, whilst the highly specialised nature of enzyme 

 action points to a more intimate combination with the sugar. The 

 differences are differences only of degree. 



[Papers published since 1900 on this subject and those appearing' in 

 the future are to be found classified together in the D (Chemistry) volu°mes 

 of the ' International Catalogue of Scientific Literature,' under the head 

 ings D 1820, Hydrolysis of Cane-sugar, and D 7090, Hydrolysis.] 



Biblwrjmphy of Literature of , Sugar Hydrolysis, 



Reference 

 ' MiMuoiics do TAcadcmic,' 2. 

 ' Ann. Chim. Phys.,' 52, p. 72. 

 'Memoires de I'Ac.idumie,' 13, p. .39 (read 188"') 

 ' I\[t'nioiios de I'Acadt'mic,' ].->, p. !k; (read 1836) 

 ' l*>VU,i4. Ann. Clicni.,' 81, pp. 413 nnd 490 



(Ost wald's ' Klas.sikcr," No. 29.) 

 • Comptcs Rendus,' 39, p. 914. 



' Ver$l. Kon Ac. ran Wet., Amsterdam, 1903, 12, p. 970. 



