Catechol Oxidase Lab Report

Inhibiting the Action of Catechol Oxidase

By Ashleen

I. Introduction

The purpose of this experiment was to see if phenylthiourea (PTU) is a non-competitive or competitive inhibitor. Catechol, a phenolic compound found in the potato extract used will play the part of the substrate. Competitive inhibitors are known to bind to the active site of an enzyme and mimic the job of a substrate. This in turn causes the substrate to compete for a position at the active site and increase the concentration of substrate but the inhibitor is still at a constant level. If PTU were a competitive inhibitor the test tube carrying the extract would turn dark brown. Non- competitive inhibitors are known to bind on the enzyme and prevent the substrate from attaching

itself to the active site. The inhibitor does not match the shape of the enzyme which is why when it attaches it blocks off the passage way for the substrate. If PTU were a non-competitive inhibitor then the test tube would stay a clear color. That is why we tested the Catechol using three different tubes leaving the 3rd tube to be the control since it does not contain any PTU.
II. Materials and Methods
In this experiment three tubes were placed on a tube rack labeled 1, 2, and 3. For all three tubes, 5mL of water were added using a pipette. However, tubes 1 received an extra .05mL of water and tube 3 received an extra 1mL of water. Using a different pipette, .05mL of potato extract was added to all three tubes. After that a new pipette was used and for tubes 1 and 3 .05mL of Catechol was added while tube 3 received 1mL of Catechol. Lastly, using a different pipette, tubes 1 and 2 received .5mL of PTU.