RECIPROCAL CATALYSIS 447 



these are, in general, present in unequal concentrations, the equi- 

 librium between the forward and reverse reactions of protein 

 hydrolysis must be shifted. Since, however, for every shift in 

 equilibrium, there must be a corresponding expenditure of energy, 

 the equilibrium between the anhydrous and hydrated forms of the 

 enzyme must also be shifted by the protein; just as the enzyme 

 accelerates the hydrolysis of the protein more than its synthesis 

 when the hydrated form of the enzyme is initially present in con- 

 siderable excess of its anhydrous form, so the protein accelerates 

 the dehydration of the enzyme more than its hydration because it 

 is initially present in great excess of its products of hydrolysis. 

 This latter fact will itself lead to a slowing of the hydrolysis of the 

 protein since the hydrated (and hydrolysis accelerating) form of 

 the enzyme is thereby diminished in concentration; as the hydroly- 

 sis proceeds, however, this effect will diminish; the products of the 

 protein hydrolysis will tend to increase the proportion of the 

 hydrated form of the enzyme to the anhydrous form, and the rate 

 of hydrolysis will increase at the expense of the rate of synthesis. 

 Ultimately, it is evident that a condition of equilibrium must be 

 reached in which the station of equilibrium between the protein 

 and its products is shifted further in the direction protein > 

 products than its position in the absence of the enzyme, while the 

 station of equilibrium between the hydrated and anhydrous forms 

 of the enzyme is shifted further in the direction hydrated form 

 anhydrous form than its position in the absence of the protein. 

 This position of equilibrium will depend, obviously, upon the total 

 concentration of the enzyme and of the substrate, respectively, 

 and once attained, a further addition of substrate would reinaugu- 

 rate the hydrolysis of protein, it is true, because the active mass of 

 hydrolysable protein would thus be increased, but it would shift 

 the point of equilibrium in the direction products > protein; 

 addition of enzyme would shift the station of equilibrium in the 

 direction protein > products, as has been found by Bayliss and 

 others (4) (68). This latter statement, however, holds good only 

 while the water in the system is in great excess of the enzyme, so 

 that varying concentration of the enzyme does not appreciably 

 affect the proportion subsisting between the hydrated and anhy- 

 drous forms at equilibrium in the absence of proteins. If, however, 

 the enzyme be very concentrated, then the proportion of water to 

 enzyme (Cf. Eq. (D)) will appreciably affect the equilibrium be- 



