CONDITIONING FACTORS 471 



action, but where the concentration of the enzyme increases 

 the reaction obeys the law of mass action up to a certain point. 



Similar results were obtained by Adrian Brown * in the 

 study of the action of invertase on cane sugar ; he also ex- 

 presses the view that, in the case of alcoholic fermentation 

 and other enzyme actions which do not apparently conform 

 with the law of mass action, the exceptional action " is due 

 to a time factor accompanying molecular combination and 

 change which limits the influence of mass action . . , this 

 theory demands not only the formation of a molecular com- 

 pound of enzyme and reacting substance, but the existence of 

 this molecular compound for an interval of time previous to 

 final disruption and change." 



Similarly E. F. Armstrong f in studying the action of lac- 

 tase and maltase upon their respective sugars found that 

 while the reaction was in the main logarithmic, both the 

 initial and final stages were linear. 



The law of mass action only is applicable at those stages 

 where the concentration of the enzyme is more or less equal 

 to that of the substrate. As the relative concentration of 

 the enzyme increases, the activity falls off and other laws 

 have been propounded to express the rate of reaction. 



4. INFLUENCE OF END PRODUCTS. 

 The velocity of enzyme action may be retarded by the 

 interference of an end product of the reaction. Thus the 

 alcohol produced by the fermentation of sugar by yeast ulti- 

 mately stops the reaction, and the same applies to the pro- 

 duction of acetic acid by Mycoderyna aceti. The hydrolysis 

 of amygdalin is retarded by the addition of glucose, benzalde- 

 hyde or hydrocyanic acid, which are products of the reaction. 

 Similarly glucose interferes with the action of maltase. These 

 retarding influences are due to various causes ; the specific 

 action of the end product on the organism, the alteration of 

 the hydrogen ion concentration, and mass action. The subject 

 is intimately connected with the action of paralysers. 



* Adrian Brown : " J. Chem. Soc. Lond.," 1902, 81, 379. 

 t Armstrong : " Proc. Roy. Soc. Lond.," B., 1904, 73, 500, 516, 526 ; 

 74, 188, 195. 



