EFFECTS OF TEMPERATURE, DIELECTRIC CONSTANT 

 AND DIFFUSION RATES ON FORMATION OF THE 

 INTERMEDIATE COMPOUND OF CATALASE 

 AND HYDROGEN PEROXIDE 



Eugene Ackerman, Greenville Kash Strother and Robert 

 Lewis Berger,^ Physics Department, Pennsylvania State 

 University, University Park, Pennsylvania 



V^atalase is an enzyme, found widely distributed throughout living mat- 

 ter. The speed with which this heme protein decomposes hydrogen perox- 

 ide led to its early discovery. However, the details of its action were only 

 elucidated since the last war, due primarily to the studies of Chance and 

 his co-workers. These results have been summarized by Chance (1) ; only 

 the necessary details will be reviewed below. The reaction of catalase with 

 hydrogen peroxide has the advantage of involving only one species of a 

 small inorganic molecule reacting with a large heme protein. This reaction 

 is desirable since both the enzyme and substrate have characteristic ab- 

 sorption bands in the visible and ultraviolet. Spectrophotometric record- 

 ing of the time course of the reactions is therefore possible. 



This paper deals with what happens in a biological reaction on a molecu- 

 lar and submolecular level. Evidence for this can be found in the varia- 

 tion of reaction rates with the physical properties as temperature, dielectric 

 constant and coefficient of viscosity. 



theory 



From temperature studies one can find a characteristic heat of activa- 

 tion AHa , provided one is measuring the rate of a single reaction. If it is 

 not controlled by the diffusion rate of the reactants, then AHg may be re- 

 garded as a fundamental property of the molecules involved. It has been 

 stated (2) that if a reaction has a heat of activation around 12 Cal/mole, 

 it is probably not diffusion controlled, whereas if AH., is around 3-4 Cal/ 

 mole, the reaction is diffusion controlled. The catalase-hydrogen peroxide 

 reaction is interesting since AHa for the overall reaction varies from 1.4 

 to 2 Cal/mole (3). 



If the reaction involves one or more charged molecules, one in general 

 may expect the rate to vary as the dielectric constant (2) . One difficulty 



^ Present address : Department of Colloid Science, Free School Lane, Cambridge, 

 England. 



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