1904] 



Studies on Enzyme Action. 



503 



of maltose. E. Fischer and the author* had meanwhile shown that the 

 enzymes lactase and emulsin both acted reversibly. 



English workers appear to have overlooked the work done by 

 Tamman in 1892,f who studied with great care the action of emulsin 

 on the two glucosides salicin and amygdalin, as well as that of invertase 

 on cane sugar. He came to the conclusion that the rate of change was 

 retarded by the products of degradation but could detect no sign of 

 reversion ; he even went so far as to express the opinion that enzymes 

 did not act reversibly. He insisted, however, that their action was 

 incomplete. 



In dealing with problems of enzyme action, the probability that the 

 extract used contains several enzymes cannot be lost sight of, since it 

 is known that in yeast extract, for example, at least three sucroclastic 

 enzymes are present together with a proteoclast in amounts which 

 vary in different yeasts. It is at least conceivable that, in those cases 

 in which reversion has been observed, the hydrolysis is conditioned by 

 one enzyme and the synthesis by another. It will be obvious, 

 therefore, that the field for investigation is a very wide one and that 

 our knowledge of enzymes is of a most incomplete and unsatisfactory 

 character. 



The present communication deals with the problem of the rate at 

 which change proceeds during the earlier period, when the products of 

 hydrolysis are present in relatively small proportions. 



The results obtained not only justify the extension to enzymes 

 generally of the view put forward by Horace Brown and Glendinning 

 in explanation of the action of diastase and invertase, but also make it 

 possible to explain cases in which the departure from the law of mass 

 action is in a direction contrary to that considered by these authors ; 

 the influence exercised by the products of change, which was not taken 

 into account by them, will also be considered. The action of acids is 

 compared with that of enzymes in a separate communication. 



Preparation of Enzyme. — The enzymes considered are lactase, emulsin 

 and maltase ; the first two of these both condition the hydrolysis of 

 milk sugar but the last affects only maltose. Unfortunately no way 

 has been devised hitherto of working with a known amount of enzyme ; 

 the nearest approach to a satisfactory method is to prepare a fresh 

 extract for each series of experiments under conditions as nearly 

 uniform as possible. Far too little care is sometimes given to this 

 operation, the importance of working rapidly and at a suitable tempera- 

 ture being commonly neglected. The following is a description of 

 the methods adopted in the experiments referred to in this com- 

 munication. 



Lactase. — Ten grammes of Kephir grains were very vigorously 



* « Ber.,' 1902, vol. 35, p. 3144. 



f ' Zeit. Physiol. Cheui.,' vol. 16, p. 271. 



