424 



SCIENCE 



[N. S. Vol. XLVII. No. 1218 



Since en^iymes manifest their actions by 

 increasing the velocities of chemical reac- 

 tions, a large amount of work has been 

 done in studying the kinetics of such reac- 

 tions. The actual results obtained from 

 such studies in so far as light has been 

 thrown on the chemical nature of enzymes 

 has been disappointingly meager. In fact 

 the results which might be expected from 

 such studies have been in large measure 

 unsatisfactory. This may be shown by a 

 brief survey of some of the work on the 

 kinetics of invertase action, to which, from 

 this point of view, more attention has been 

 paid than to any other enzyme action. In- 

 vertase, as is well known, hydrolyzes cane 

 sugar to form glucose and levulose. 'Sul- 

 livan and Tompson^ in 1890, as a result 

 of the study of the kinetics of this reaction, 

 concluded that the reaction was of the 

 first order, the velocity being proportional 

 to the concentration of the cane sugar. 

 Duclaux* in 1898, Brown'* and also Henri" 

 in 1902, found that the velocity of this re- 

 action was not of the first order as shown 

 by the lack of constancy of the velocity co- 

 efficients. Henri^ suggested in 1905 that 

 because of the colloidal nature of enzymes, 

 the reaction belongs to a two-phase system 

 to which the simple mass law is not appli- 

 cable in the given manner. Hudson' in 

 1908 as a result of some new work in which 

 the mutarotation of the invert sugar was 

 taken into account, found that the hydrol- 

 ysis of cane sugar in the presence of in- 

 vertase gave velocity coefficients that were 

 constant when calculated by the unimolecu- 



3 O 'Sullivan and Tompson, J. Chem. Soc, 57, 834 

 (1890). 

 *Duclaux, Ann. Inst. Pasteur, 12, 96 (1898). 



5 Brown, J. Chem. Soc, 81, 375 (1902). 



6 Henri, Z. PhysiJc. Chem., 39, 215 (1902). 



7 Henri, Z. PhysiJc. Chem., 51, 19 (1905). 



8 Hudson, J. Am. Chem. Soc, 30, 1160, 1564 

 (1908). 



lar formula. He therefore claimed to have 

 confirmed the conclusions of 'Sullivan 

 and Tompson. Michaelis and Menton' in 

 1913 disagreed with Hudson in attempting 

 to express the velocity of the reaction as a 

 simple logarithmic function of the sugar 

 concentration and elaborated the view of 

 Henri of the two-phase system and forma- 

 tion of an intermediate compound. Bay- 

 liss^" in 1911 developed the view of such 

 intermediate compounds as adsorption 

 compounds and concluded that the rate of 

 enzyme action was a function of the 

 amount of adsorption compound in exist- 

 ence at any particular time. Nelson and 

 Griffin^^ in 1916 developed the two-phase 

 system view of invertase action and in 

 1917, as a result of an extended series of ex- 

 periments, Nelson and Vosburgh" sum- 

 marized and stated clearly the present 

 status of the problem of the kinetics of in- 

 vertase action. Their conclusions may be 

 stated briefly as follows : 



I. The velocity of inversion is directly 

 proportional to the concentration of the in- 

 vertase. 



II. The velocity is nearly independent 

 of the concentration of the cane sugar in 

 the more concentrated sugar solutions, 

 while in very dilute sugar solutions the ve- 

 locity increases with increase in concentra- 

 tion of the substrate and finally reaches a 

 maximum. 



III. The results obtained agree with the 

 heterogeneous reaction view and contradict 

 the claim that the kinetics of invertase ac- 

 tion conform to the unimolecular law for 

 homogeneous reactions. 



Michaelis and Menton, Biochem. Z., 49, 333 

 (1913). 



loBayliss, Proc. Boy. Soc. London (B), 84, 90 

 (1911). 



11 Nelson and Griffin, J. Am. Chem. Soc, 38, 

 1109 (1916). 



12 Nelson and Vosburgh, J. Am. Chem. Soc, 39, 

 790 (1917). 



