Two Factors that Affect the Enzyme Activity

Enzyme is a protein molecule that takes on a particular shape which enables them to speed up biochemical reactions within the organisms, therefore behaving as a catalyst. It can also be used in industrial and medical contexts. Bread making, cheese making and beer brewing all depend on the activity on enzymes, and enzymes can be inhibited if their environment is too acidic or too basic. The rate of action of an enzyme is highly dependent on many key variables, including enzyme pH stability, temperature, etc.

A pH environment has a significant effect on enzymes. It can affect the intramolecular forces and change the enzyme's shape -- potentially to the point where it is rendered ineffective. With these effects in mind, typical enzymes have a pH range in which they perform optimally. For example, α amylase, which found in the mouth, operates most effectively near a neutral pH. However, lipases operate better at more basic pH levels. Buffer systems built into most organisms prevent pH levels from reaching the point where essential enzymes are rendered ineffective. If an enzyme is rendered ineffective by pH level, adjusting the pH can cause the enzyme to become effective again.

We think of pH as an indicator of acidity. Vinegar is weakly acidic, so its pH is about 4, while baking soda is alkaline, and its pH is about 8. The neutral solution, pH 7. Most of our body fluids have a neutral pH of about 7.2, so human enzymes have the highest activity at this pH.

On a molecular level, pH can be thought of slightly differently. A low pH means there are a lot of extra protons in a solution, while a high pH means there are a lot of hydroxide ions -- oxygen and hydrogen together. At low pH, the positive charges of the protons in the solution will be attracted to regions with a negative charge, and they'll latch on. At high pH, the OH ions, which are negative, will seek out positive charge and latch on.

Enzymes bring component atoms or molecules together in just the right way to lower the activation energy. They're able to do this because of how they're shaped. The shape of a protein depends in part on electrostatic attraction between its different parts. For example, some parts have a slightly negative charge, and some slightly positive, so those regions of the protein are bent toward each other.

In solutions of low pH, the extra positive charges connect to negative regions of proteins. In high pH solutions, the extra negative charges latch on to a protein's positive regions. When they latch on, the electrostatic attraction is eliminated and the protein changes shape. Because an enzyme activity depends upon its shape, it will slow down, then eventually stop working when the pH gets too low or too high.

Enzyme activity is closely related to temperature. As temperature increases, enzyme activity also increases correspondingly because there is an increase in the number of collisions between the reacting molecules and the enzymes. Increased temperatures further lead to peak enzyme activity. For human enzymes, this peak temperature is about 98.6 degrees Fahrenheit, which is our body temperature. Any further increase in temperature will lead to a decrease in enzyme activity. This is due to the denaturation of the enzyme protein, that is, the breaking of molecular bonds within the protein. When these bonds are broken, the shape changes and it no longer functions properly as a catalyst.

Enzymes work by lowering the activation energy of a chemical reaction. You can think of a chemical reaction as something like putting a beanbag into a bucket, except that there's a 10-foot wall between the beanbag and the bucket. You can climb over the wall and put the beanbag in the bucket, but if you had the help of an enzyme, the wall would only be 2 feet high instead of 10 or 100 or 1000. The final result is the same no matter how high the wall is, but you'll be able to put a lot more beanbags in buckets if the wall is low. The same with enzymes: the final chemical product is the same with or without an enzyme, but many more reactions will happen if the enzyme is there.