JOHN H. NORTHROP 



which accelerates all the reactions. If, however, only the tube connecting 

 A and B .s opened the level of B will rise to position . and no measu able 

 change w.ll occur m the levels of C, D. and E during this time 



The preceding example resembles more or less the hydrolysis of pro- 

 ems hydrolysts with acid leads to complete hydrops and esu tfht 



also lead only to ammo aads at equdibrium under the same conditions 

 Pepsm or trypsnt, however, increase the rate of hydrolysis of some 

 protem hnkages much more than others, so that for all praciical purpose 

 he reacfon stops before any amino acids are formed, although h 

 still far from equilibrium. " 



Enzymes as Theoretical Catalysts 

 The agreement between enzyme reaction and catalytic theory has been 

 much more fully confirmed in connection with carbohydrates and esters 

 than with proteins. 



The first experimental synthesis by an enzyme was reported by Croft 

 Hill, who found that a disaccharide which he thought was maltose was 

 formed by the action of maltase on concentrated glucose solutions The 

 substance however, was eventually identified by Emmerling as iso- 

 maltose which is formed, under the same conditions, by acid catalysis 

 Iso-maltose is not hydrolyzed by maltase and this fact led Armstrong 

 to suggest that enzymes synthesize substances which they do not hydro- 

 lyze. This assumption is contrary to the law of catalysis since it predicts 

 that the direction of the reaction, and, hence, the equilibrium condition 

 vary with the catalyst. It was found later that the ''maltase" prepara' 

 tion used by Croft Hill contained emulsin which does hydrolyze iso- 

 maltose and, hence, also synthesizes it. This is one of many examples of 

 the confusion caused by the use of impure enzyme preparations 



Bourquelot studied the simpler case of glucoside hydrolysis and syn- 

 thesis and found in several cases that enzymes caused the reaction to 

 proceed towards the equilibrium point from either side. This furnished 

 experimental proof of the statement that enzymes do not change the 

 equilibrium point. 



Kastle and Loevenhart showed that the hydrolysis of esters by lipase 

 also agrees with theory. 



Pottevin found that pancreatic lipase synthesizes esters from oleic 

 acid and methyl alcohol and that the equilibrium condition was inde- 

 pendent of the concentration of enzyme. (For review of the older litera- 

 ture see Euler, 1925, p. 295 ; and BayHss, 1925.) 



