What does an enzyme's absorbance mean?

Question

In an experiment we did in a lab class, we put the enzyme Beta Galactosidase (b-gal) in a test tube with ONPG, a lactose-mimicking chemical. We put the tube in a Spec 20 to measure the absorbance. As the ONPG was broken down by b-gal, the solution in the tube turned yellow.
We tested this at several different temperatures and measured the absorbance at 15 seconds. At low temperatures, the absorbance was very low. Warmer temperatures showed a higher absorbance. However, temperatures that were "too high" showed a lower absorbance.
My question is, what does absorbance even mean? Why do we see this trend in the enzyme data?

Answer 1

When you are measuring the absorbance in this case, you are measuring the product that the enzyme produced from the ONPG. When this enzyme acts on ONPG, is produces a yellow product. So, the higher the absorbance, the more product was produced, which means the enzyme was working more rapidly.

Every enzyme has an optimal temperature for its activity. When colder, the enzyme (like all chemical reactions) occurs more slowly. When the temperature is too high, the enzyme begins to "denature". That means that it begins to lose its normal shape and structure, and cannot function any longer.

Hope this helps.

Answer 2

High Absorbance Means