262 



NA TURE 



[July i i, 1907 



The actual change of constitution of the liquid in the 

 crystallising mixture was traced by means of the refractive 

 index. 



These experiments show that a binary mixture has, !n 

 general, four freezing points. For example, the mixture 

 containing go per cent, salol may yield crystals of sa'ol 

 by inoculation at 38°, and by stirring at 28° ; crystals cf 

 betol by inoculation at i/J", and by stirring at ioi°. 



The actual temperatures of crystallisation in binary 

 mixtures are given by the supersolubility curves. 



May 23. — " Studies on Enzyme .Action. X. — The Nature 

 of Enzymes." By Henry E. Armstrong and E. Frankland 

 Armstrong. 



The study of enzymes has now reached a stage at which 

 it appears to be desirable to consider what is established 

 and to direct attention to some of the principal issues 

 which remain to be elucidated. The action which each 

 enzyme e.xereises is clearly specific and limited to com- 

 pounds of a particular type ; ihe apparent exceptions to 

 this statement in the case of sucrorlastic enzymes have 

 been investigated and eliminated : there is little doubt that 

 maltase is capable of hydrolysing a-glucosides alone, whiKt 

 emulsin hvdrolyses only j3-giucosides. Further experiments 

 have been' made with carefully purified materials to ascer- 

 tain what substances control Ihe action of each sucroclasti." 

 enzyme ; the evidence that enzyme and hydrolyte must be 

 in complete correlation appears to be little short of absolu:o. 



A special study has been made of the hydrolysis of cane 

 sugar by invertase : apparently, glucose and fructose alone 

 retard the action of this enzyme ; it would seem to 

 follow that it is so constituted that it can adapt itself 

 to both sections of the biose. Cane sugar, though a 

 derivative of a-glucose, is not a simple o-glucoside, nor is 

 it an a-fructoside ; consequently there is little room for 

 doubt that the action of invertase is altogether peculiar and 

 that the enzyme extends its influence over the whole of 

 the cane-sugar molecule. Maltose and lactose differ from 

 cane sugar in that they are hydrolysed by enzymes which 

 also act on the corresponding simple glycosides. 



It is conceivable that the enzymes themselves are subject 

 to hydrolysis and simplification — in other words, that a 

 biose may give rise to a monase. The existence of monases 

 in admixture with biases is therefore to be expected. 

 There can be little doubt that the sucroclastic enzymes arc 

 products of hydrolytic changes in the protoplasm con- 

 ditioned by enzymes — mainly proteoclasts. 



" Studies on Enzyme Action. IX. — The Enzymes of 

 Yeast : Amygdalase." By R. J. Caldwell and S. L. 

 Courtauld. 



Amygdalin, which on complete hydrolysis yields two 

 molecular proportions of glucose, is only partially 

 hydrolysed by the enzymes extracted from dried yeast, 

 mandelonitrile glucoside and glucose being formed : — 

 C' H,CH(CN")0— C,,H,,0,„-fH..O ^ 



'C.HjCH"(CN)0— C,H„05-fC,H,,0.. 

 The enzyme which effects this decomposition is specific, 

 but being accompanied by maltase has been generally sup- 

 posed to be identical with it. This conclusion, however, 

 appears unwarrantable in view of the evidence recently 

 advanced by the authors that amygdalin is not a derivative 

 of maltose, and in the light of recent work on the specific 

 character of the enzymes (E. F. Armstrong). 



Systematic experiments with yeast extracts led to the 

 conclusion that true maltase is without action on 

 amygdalin, for the maltase could be destroyed by heating 

 at 50°, whilst the activity towards amygdalin was un- 

 impaired. Proof was thus obtained of the existence of a 

 specific enzyme not hitherto recognised as a constituent 

 of yeast, which is the active agent in the separation of 

 glucose from amygdalin. This enzyme, "amygdalase," is 

 present in larger proportion in top yeasts than in bottom 

 yeasts, and appears to be equally well extracted at all 

 temperatures from 15° to 45°, whereas for the extraction 

 of maltase there is a distinct optimum temperature depend- 

 ing on the variety of yeast. 



Although completely freed from maltase by heating at 

 50°, yeast extract retains not only its power to hydrolyse 

 amygdalin, but also a diminished activity towards methyl- 

 n-glucoside, and unaltered activity towards cane sugar. 

 The inference that methyl-a-clucoside is attacked by the 



NO. 1967. VOL. 76] 



two enzymes maltase and amygdalase cannot well be 

 disputed, particularly as amygdalin is more slowly hydro- 

 lysed in presence of methyl-o-glucosidc, whereas maltose 

 has no influence. The alternative explanation is that there 

 is yet another a-glucasc existing side by side with maltase 

 and amygdalase. The enzyme which attacks amygdalin 

 is not identical with invertase as Marino and Sericano 

 have recently declared, for a high temperature (60°) quickly 

 destroys amygdalase, leaving active invertase in solution. 



Amygdalase, like maltase and invertase, is present in 

 the yeast in the form of a " zymogen-" or more complex 

 proteid molecule. This zymogen can be dissolved out at 

 0°, and its hydrolytic activity developed by heating the 

 solution for a short time at 45°. Unlike maltase, 

 amygdalase is not destroyed during autolysis of yeast, but 

 may be precipitated with the invertase by means of 

 alcohol. 



June 20. — " Studies of the Processes operative in Solu- 

 tions." 



(2) The Displacement of Chlorides from Solution by 

 Alcohol and by Hydrogen Chloride. By H. E. Arm- 

 strong, Dr. j. \'. Eyre, A. V. Hussey and W. P. 

 Paddison. 



(3) The Sucroclastic Action of Nitric Acid as Influenced 

 by Nitrates. By R. Whympsr. 



(4) The Hydrolysis of Methylic Acetate in Presence nf 

 Salts. By H. E. Armstrong and J. A. Watson. 



(5) The Discrimination of Hydrates in Solution. I\v 

 H. E. Armstrong and R. J. Caldwell. 



(2) The effect of different proportions of the non-electro- 

 lyte alcohol and of the electrolyte (in solution) hydrogen 

 chloride in displacing ammonium, sodium and potassium 

 chlorides from their saturated solutions has been deter- 

 mined and the proportion of water calculated which it 

 may be supposed is withdrawn by the precipitant in each 

 case. The results afford an interesting picture of the state 

 of the salts in the various solutions ; in particular, th<-y 

 show that sodium and potassium chlorides are present in 

 saturated solutions in an easily precipitable, slighlly 

 hydrated form and that they pass into a more soluble anrl 

 niore hydrated form as the amount of precipitant is 

 increased. Except that alcohol has less dehydrating power 

 than hydrogen chloride, no distinction can be drawn 

 between the two as precipitants of chlorides. 



(3) The method developed in part i. of these studies by 

 R. J. Caldwell has been applied to nitrates, i.e. the 

 average concentrating effect which .i number of these salts 

 produce has been determined by hydrolysing cane sugar 

 with nitric acid in their presence and ascertaining the 

 extent to which the solution must be diluted in order to 

 reduce the rate of change to the value which it has when 

 the salt is not present. The average degree of hydration 

 deduced for the various salts is as follows : — 



AgXOj.sH.O. 



NH,N0,.7H,0. 



K\0,.8H.O." 



NaNOj.ixH.O. 



LiN0,.i3H/0. 



Sr(N03),.iSH.O. 



(4) To ascertain whether the method followed in (1) and 

 (3) of these studies can be applied to hydrolytes other than 

 cane sugar, the investigation has been extended to the 

 hydrolysis of methylic acetate by chlorhydric acid in 

 presence of various chlorides. The results arrived at are 

 as follows : — 



NH,C1.5H,0. 



KCI.8H.Or 



NaCl.ioH,. 



BaCL.iSH.O. 



CaCh.2oH,0. 



These values are slightly lower than those deduced with 

 the aid of cane sugar. It is suggested that the chlorides 

 enter to some extent into competition with the acid for 

 the ethereal salt and that, consequently, they partially 

 prevent hydrolysis. Nitrates have a slill greater effect in 

 competition with nitric acid, the apparent hydration! 

 values being NH^N0,.2H,O, LiNO,.oH,0, KN0,.iH„0 

 NaN0,.3H,0. 

 I (5) The results arrived at in these studies and in those 



