238 E. Margoliash and A. Schejter 



H2O2 1 to total active enzyme haematin, defined by Chance (1953), and repre- 

 sented by the symbol n, could be defined in the above system as : 



'' '^' =n (1) 



E — q — q" k^s + k^^a 



considering k^ to be negligible with respect to k^. 



The reversible inhibition reaction (c) could be formulated : 



{E-p-q' -q")i = q'K, (2) 



The irreversible inhibition reaction (d) could be formulated: 



5 = A„,- (3, 



Suitable transformations of equations (1) and (2), eliminating^' and solving 

 for p gave : 



{E - q")K, 



p = '- (4) 



1 +-^ 



'- 1 



n 



Introducing this value for p in equation (3) and integrating between the 



limits and t for the time, and and q" for the irreversibly inhibited enzyme 



concentration gave : 



E — q" knKz, 

 2-3 log —-^= '-^ t (5) 



^ 1 + ^ 



^-1 



n 



Representing the coefficient of t in the above equation by X one obtains : 



2-3 1og-^^= -Ar (6) 



in which A is therefore the first order reaction constant for the irreversible 

 inhibition of catalase, and has the following value: 



;. = ^-f (7) 



1 + -= 

 '--\ 



n 



