Enzyme Catecholase's Effect on Catalyzing Catechol to Benzoquinone

Enzymes are defined as proteins that catalyze, or speed up chemical reactions Enzymes work on molecules known as substrates, and change them into different molecules. Enzymes have been used in a variety of ways since their discovery from the making of high-fructose corn syrup by processing starch into sugar (2) to manipulating DNA for use in PCR reactions and tissue browning. Most enzymes are very specific as to which substrates they work on (3).

The reason enzymes are specific to their substrates has been suggested to be because of the “lock-and-key” model, where both the enzyme and substrate have specific characteristics that fit perfectly into one another; however, the interactions are constantly reshaped, owing to the flexibility of enzymes’ structures (4).

An enzyme’s catalytic activity is also affected by many factors including environmental conditions such as temperature and pH. Tissue browning in fruits and vegetables results in a loss of quality (5, 6) and it is caused by enzymatic reactions.

For example, in apples and bananas, browning occurs because of the reaction between catechol and oxygen, catalyzed by the enzyme catecholase, resulting in the production of a compound called benzoquinone (7).

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Potatoes also contain, among other enzymes, catecholase. While catechol, the substrate is colorless, benzoquinone, the product, is reddish-brown in color, resulting in changed absorbance. Thus, absorbance can be a measure of the enzymatic reaction. In this study, the effect of increasing the concentration of catecholase on the rate of conversion of catechol into benzoquinone was examined by means of fluorescence.

Materials and Methods Four small test tubes were labeled with a grease pencil.

Increasing amounts of potato extract, the source of catecholase, were added to each tube, along with water, to a total final volume of 4 mL. The tubes were sealed with parafilm, and inverted to mix the solution. Next, 2 mL of catechol was added to each tube, and quickly inverted after adding the substrate. Each tube was read at 1, 3, 5, 7, and 9 minutes and absorbance data was recorded on a spectrophotometer at a wavelength of 540 nm.