580 REPORT— 1902. 



therefore, the more probable that isomaltose should be formed by the action of 

 enzymes, as their behaviour in otlier respects resembles that of acids. Unfortu- 

 nately nothing is known as to the relationship of isomaltose to maltose, and it is 

 impossible to say whether they are merely the n- and /3-gluco8ide forms, or whether 

 they differ as regards the carbon atom to which the glucoside linkage is attached. 



The author has been engaged in studying lactase in conjunction with Professor 

 E. Fischer, and they have been able to demonstrate that this enzyme is one of 

 those which are capable of inducing synthetical changes. 



It was found that, whereas the action of lactase on milk-sugar was at first 

 hindered and ultimately stopped entirely by the presence of the monosaccharides 

 to which it gives rise, when the amount of these was further increased a change in 

 the reverse direction took place. Accordingly the enzyme was kept for some time 

 at 3o° in a concentrated solution containing equal parts of galactose and glucose, 

 toluene being added as an antiseptic. Botb the reducing power and the optical 

 rotatory power of the solution diminished steadily, and the phenylhydrazine test 

 showed that a sugar was present capable of forming an osazone wliich was easily 

 fioluble in hot water. The tests, in fact, united in proving that a disaccharide had 

 been produced. After three weeks the rotatory power of a 60 per cent, solution 

 had fallen by about 16-20 per cent., indicating that roughly 20-25 per cent, of the 

 glucose had been convei'ted into disaccharide ; this conclusion was contirmed by 

 the change in the reducing power. The isolation of the sugar in a pure state has 

 not yet been effected. 



The properties of its phenylosazone resemble tho.se of phenyllactosazone. More 

 light has been thrown on the nature of the sugar by the study of its behaviour 

 towards other enzymes. Having proved that the sugar — which has been termed 

 provisionally Isolactose — is unfermentable by ' top yeast,' the solution, obtained in 

 the manner described, was boi!ed, diluted, and subjected to fermentation in order to 

 remove the major portion of the unchanged monosaccharides : it was then concen- 

 trated, and its behaviour studied towards ' bottom ' yeast, emulsin, and kefir 

 lactase. All the usual precautions were observed, the extent to which changes 

 took place in the solution was ascertained by determining its reducing power and 

 its rotatory power, when possible, and especially by means of the phenylhydrazine 

 test. 



In this way it was proved that, whilst isolactose is entirely fermented by ' bottom 

 yeast,' and hydrolysed by lactase, emulsin is without any action upon it. Tabulating 

 the behaviour of the natural and synthetic sugars, it is obvious that the two are 

 distinguished by their behaviour towards bottom yeast and emulsin ; their rela- 

 tionship is, therefore, of the same order as that which obtains between the a- and 

 /3-alkyl-glucosides. 



Top Yeast Bottom Yeast Emulsin Lactase 



Milk-sugar . . unchanged unchanged hydrolysed hydrolysed 

 Isolactose . . unchanged fennented unchanged hydrolysed 



It is, at any rate, certain that milk-sugar is not formed, so that in the case of 

 lactase, as in that of maltase, a sugar isomeric with that normally hydrolysed by 

 the enzyme is obtained as the product of its synthetic activity. 



Lactase also exercises a reversible action, though to a much less extent, in a 

 concentrated solution of glucose. In this case, also, a disaccharide is formed which 

 is characterised by yielding a very soluble phenylosazone. On the other hand, 

 little or no synthetical action is effected by lactase in a solution of galactose. 



Finally, experiments carried out in an exactly similar manner with emulsin 

 show that this enzyme )s also capable of effecting synthetical changes, and that it 

 acts in a particularly rapid manner. The maximum of reversion is effected in a 

 concentrated (50 per cent.) solution containing equal parts of glucose and galactose, 

 an equilibrium being arrived at when about 20 cent, of disaccharide is present. 

 Reversion also takes place in a concentrated solution of glucose under the 

 influence of emulsin. The products afford phenylosazones which are easily soluble 

 in hot ^yater, and are not fermented by top yeast, but easily by bottom yeast. 



It may therefore be regarded as established that the enzymes which induce the. 



