MadSci Network: Biochemistry
Query:

Re: Does the enzyme Catalase have more than one optimum pH?

Date: Tue Oct 3 16:30:00 2000
Posted By: Alvan Hengge, Faculty, Chemistry and Biochemistry, Utah State University
Area of science: Biochemistry
ID: 969810703.Bc
Message:

Many enzymes can exhibit a different pH optimum under different conditions.  
For example, the identity of the substrate can make a difference.  The 
addition of cosolvents such as alcohols to the solution can affect the pH 
optimum for catalysis.  For enzymes that utilize metal ions, the identity of 
the metal ions that are available can affect the pH optimum.  Temperature 
can also make a difference.  The presence of inhibitors can also make a 
difference.

The question of why this happens can be complicated.  When you determine the 
pH dependency you are actually titrating catalytic groups either on the 
substrate, on the enzyme, or on the enzyme-substrate complex.  Any change in 
the experimental conditions, or in the nature of the substrate, that alters 
the pKa of one of the catalytic groups will result in a change in either the 
shape of the pH-rate dependency, or in the position of the pH optimum. 

Here is a web site that discusses the effect of pH on enzymatic activity:
 http://www.worthington-biochem.com/introBiochem/effectspH.html

 



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