ENZYMES 189 



activity after a time; in solution they all deteriorate more or less 

 rapidly. We do not know whether this depends upon purely me- 

 chanical variations, or whether it is associated with a chemical 

 change. For the former view we have the fact that many enzyme 

 solutions may be inactivated by mere shaking; a rennet solution, for 

 instance, need be violently shaken only two minutes in a test tube 

 in order largely to deprive it of its capacity to coagulate milk. Even 

 E. ABDERHALDEN and M. GUGGENHEIM* had observed that tyro- 

 sinase, expressed yeast juice, and pancreatic juice had their activity 

 partially inhibited by shaking them for 24 hours. A. O. SHAKLEE 

 and S. J. MELTZER* found the same true for pepsin and M. M. 

 HARLOW and P. G. STILES* for ptyalin. 



Quite independently in 1908, SIGNE and SIGVAL SCHMIDT-NIELSEN* 

 observed the inactivation of rennet by shaking, and subjected the 

 phenomenon to a thorough study. It was deduced from this that 

 inactivation by shaking is a surface phenomenon; the inactivation in- 

 creases with the length of time and the violence of the shaking; the 

 volume of air present, the concentration of the enzyme, and the tem- 

 perature are all influencing factors. The enzyme becomes con- 

 centrated in the foam and on the surface of the vessel employed. 

 The foam is more active than the fluid and the procedure offers a 

 possible method of concentrating enzymes. If a rennet solution that 

 has been shaken is allowed to stand, it recovers some, but never all 

 of its original activity; a portion remains irreversible. If saponin 

 is added to a rennet solution, no inactivation results from shaking 

 because saponin drives the rennet from the surface. 



Subsequently M. JACOBY and A. SCHUTZE* published an analogous 

 observation. They found that hemolytic complement (see p. 196) of 

 guinea-pig serum was inactivated by shaking it at 37 C. Reac- 

 tivation, in other words the reversibility of the process, depends 

 on the duration of the shaking. At first, only a definite fraction 

 of the complement is irreversibly inactivated by the shaking since 

 it may be reactivated by "end piece" and also incompletely by 

 "middle piece." When the shaking has been sufficiently prolonged 

 the complement is irreversibly inactivated according to RITZ. The 

 inactivation depends, according to P. SCHMIDT and LIBBER, on 

 the fact that the serum is made turbid by shaking, a foam is 

 formed into which the globulin separates, and this globulin adsorbs 

 the complement. The reactivation by "end piece" results from the 

 solution of the flocculated globulin thus liberating the complement 

 (see p. 196). To what extent the action of the alkali (from the glass) 

 assists in the inactivation has not been determined with certainty. 

 On the contrary, it seems from the data, that only a portion of the 



