Question

describe the procedure for determining the properties of the liver enzyme catalase

Answer 1

Catalase is an enzyme which breaks hydrogen peroxide into water and oxygen. Hydrogen peroxide is a very harmful byproduct of many of the metabolic reactions of our body which needs to be removed as soon it is made to prevent damage to the body. In short, it protects our system from the oxidative damage caused by reactive oxygen species. So, we divide the properties in of the catalase in three parts-

1.) Molecular weight - Weight of the enzyme can be known by running SDS- PAGE. Sodium Dodecyl Sulphate Polyacrylamide Gel Electrophoresis is a technique which is used to check the purity and molecular weight of a protein. Here, since denaturing conditions are employed for running the gel the effect of charge and structure of the protein is negated and the only determinant is the length of a polypeptide.

2.) Check Activity of enzyme- One can check the activity of catalase by Spectrophotometer by checking the absorbance at 240nm. The substrate used will be hydrogen peroxide for the reasons explained in the introduction. In control you will not add enzyme, but in test sample you will add enzyme. Both the samples - control and test will have hydrogen peroxide buffer solution. The absorbance needs to be measured at 240nm and the activity then needs to be calculated using Beer lambert law.

Please note -  One unit is the amount of enzyme which decomposes one micromole of hydrogen peroxide per min at 25°C.

3.) Other Physiochemical properties- One can check the optimum temperature and pH at which catalase works by checking the enzymatic activity at a range of temperature and pH. The temperature and pH at which maximum activity is obtained is optimum for this enzyme.