ENZYME KINETICS 



this relation would not be expected to be obeyed, since the for- 

 ward reaction would be catalyzed by enzyme activated by F 

 and the reverse reaction by enzyme activated by M. Although 

 this relation was derived in a very simple way it is applicable 

 even when the mechanism is very complicated and involves pH. 

 and buffer effects, provided only that the steady-state velocities 

 of the forward and reverse reactions are represented by the 

 Michaelis equation. The Haldane equation has been found to 

 be obeyed by the fumarase reaction over a wide range of pH 

 and buffer concentrations and offers a valuable check on experi- 

 mental values of the kinetic constants (2). 



For reactions involving more than one reactant and one 

 product (other than water and hydrogen ions) there are more 

 complicated relations between kinetic constants for the forward 

 and reverse reactions and the equilibrium constant for the over- 

 all reaction ( 1 ) . Since the form of this relationship depends upon 

 the mechanism of the reaction, it should be possible to differenti- 

 ate between certain mechanisms for coenzyme reactions by 

 means of steady-state kinetic data on both the forward and re- 

 verse reactions. 



TEMPERATURE EFFECTS 



The interpretation of apparent activation energies for 

 enzymatic reactions is considerably more difficult than for 

 simpler reactions. This is a consequence of the large number of 

 changes which may occur when the temperature of a protein 

 solution is altered. In addition to the effect of temperature on 

 individual rate constants, there will generally be effects upon 

 the extent of ionization of the protein and its interaction with 

 ions of the bufTer solution. The temperature coefficient of a 

 reaction determined without regard to these possibilities remains 

 a hodgepodge of various effects. In order to identify the various 

 participating equilibria, it would be necessary to study the effects 

 of pH, buffer concentration, etc., at a series of temperatures. 

 However, there have been relatively few studies so far in which 

 the effects of temperature on the Michaelis constant and maxi- 



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