JOHN H. NORTHROP 



247 



with the enzyme. If this were true the retardation should be less 

 the greater the concentration of gelatin, provided the relative amount 

 of inhibitor to trypsin were kept the same. Table II shows that this 

 is not the case. The amount of retardation is independent of the 

 concentration of gelatin used. The result is confirmed by the experi- 

 ment discussed below in which the concentration of inhibitor is kept 

 the same and the concentration of trypsin varied. If the inhibitor 

 combined with the gelatin, the resulting solution would act as though 



TABLE II. 



Influence of Gelatin Concentration on Retardation of Hydrolysis by Inhibiting 



Solutions. 



Control, 25 cc. gelatin of concentration noted + 1 cc. trypsin + 1 cc. 0.01 N 

 NaCl. Solution, 25 cc. gelatin of concentration noted + 1 cc. trypsin + 1 cc. 

 inhibiting solution. Temperature 33°C. Specific conductivity of all solutions 

 1.2 X 10-3 (adjusted with NaCl, and pH of 6.0 adjusted with NaOH). 



Time required for 10 points change with 1 cc. trypsin ... . , 



=: -. — , , ,- r— — r r-r-. ; : — ^—. ■ , ■■ .^ ID gelatm concentrations of 



Time required for 10 points change with 1 cc. trypsin + 1 cc. inhibitor 



* Average deviation of the mean. 



a lower concentration of gelatin had been used and the velocity would 

 still be directly proportional to the amount of trypsin added to the 

 solution. This is not the case. The fact that the inhibiting solution 

 renders trypsin more stable (when no protein is present) also shows 

 that it combines with the trypsin. 



Influence of Inactivated Trypsin. 



It was found in the case of pepsin^ that pepsin inactivated by 

 alkali took part in the equilibrium just as does the active pepsin 



3 Northrop, J. H., /. Gen. Physiol., 1919-20, ii, 471. 



