8 FACTORS AFFECTING ENZYME ACTIVITY - BIOLOGY - 2024

The factors affecting enzyme activity are those agents or conditions that can change the functioning of enzymes. Enzymes are a class of proteins whose job is to speed up biochemical reactions. These biomolecules are essential for all forms of life, plants, fungi, bacteria, protists, and animals.

Enzymes are essential in several important reactions for organisms, such as removing toxic compounds, breaking down food, and generating energy.

Representation of the enzyme Polyneuridine-Aldehyde Esterase.

Thus, enzymes are like molecular machines that facilitate the tasks of cells and, on many occasions, their functioning is affected or favored under certain conditions.

List of factors that affect enzyme activity

Enzyme concentration

As the enzyme concentration increases, the rate of the reaction increases proportionally. However, this is the case only up to a certain concentration, since at a certain moment the speed becomes constant.

This property is used to determine the activities of serum enzymes (from blood serum) for the diagnosis of diseases.

Substrate concentration

Increasing the substrate concentration increases the rate of the reaction. This is because more substrate molecules will collide with the enzyme molecules, so the product will form more quickly.

However, when exceeding a certain concentration of substrate there will be no effect on the speed of the reaction, since the enzymes would be saturated and working at their maximum speed.

pH

Changes in the concentration of hydrogen ions (pH) greatly influence the activity of enzymes. Because these ions are charged, they generate attractive and repulsive forces between the hydrogen and ionic bonds in enzymes. This interference produces changes in the shape of the enzymes, thus affecting their activity.

Each enzyme has an optimal pH at which the reaction rate is maximum. Thus, the optimal pH for an enzyme depends on where it normally functions.

For example, intestinal enzymes have an optimal pH of about 7.5 (slightly basic). In contrast, enzymes in the stomach have an optimal pH of about 2 (very acidic).

Salinity

The concentration of salts also affects the ionic potential and consequently they can interfere in certain bonds of the enzymes, which can be part of the active site of the same. In these cases, as with pH, ​​enzyme activity will be affected.

Temperature

As the temperature increases, the enzyme activity increases and, consequently, the rate of the reaction. However, very high temperatures denature enzymes, this means that excess energy breaks the bonds that maintain their structure, causing them to not function optimally.

Thus, the rate of the reaction decreases rapidly as the heat energy denatures the enzymes. This effect can be observed graphically in a bell-shaped curve, where the reaction rate is related to temperature.

The temperature at which the maximum reaction rate occurs is called the optimum enzyme temperature, which is observed at the highest point of the curve.

This value is different for the different enzymes. However, most of the enzymes in the human body have an optimum temperature of around 37.0 ° C.

In short, as the temperature increases, initially the reaction rate will increase due to the increase in kinetic energy. However, the effect of the breakdown of the union will be greater and greater, and the reaction rate will begin to decrease.

Product concentration

Accumulation of reaction products generally slows down the enzyme. In some enzymes, the products combine with their active site to form a loose complex and thus inhibit the activity of the enzyme.

In living systems, this type of inhibition is generally prevented by rapid removal of the products formed.

Enzyme activators

Some of the enzymes require the presence of other elements to function better, these can be inorganic metal cations such as Mg ²⁺, Mn ²⁺, Zn ²⁺, Ca ²⁺, Co ²⁺, Cu ²⁺, Na ⁺, K ⁺, etc.

In rare cases, anions are also required for enzymatic activity, for example, the chloride anion (CI-) for amylase. These small ions are called enzyme cofactors.

There is also another group of elements that promote the activity of enzymes, called coenzymes. Coenzymes are organic molecules that contain carbon, like vitamins found in food.

An example would be vitamin B12, which is the coenzyme of methionine synthase, an enzyme necessary for the metabolism of proteins in the body.

Enzyme inhibitors

Enzyme inhibitors are substances that negatively affect the function of enzymes and consequently slow down or in some cases stop catalysis.

There are three common types of enzyme inhibition: competitive, non-competitive, and substrate inhibition:

Competitive inhibitors

A competitive inhibitor is a chemical compound similar to a substrate that can react with the active site of the enzyme. When the active site of an enzyme has bound to a competitive inhibitor, the substrate cannot bind to the enzyme.

Non-competitive inhibitors

A noncompetitive inhibitor is also a chemical compound that binds to another site on an enzyme's active site, called the allosteric site. Consequently, the enzyme changes shape and can no longer easily bind to its substrate, so the enzyme cannot function properly.

References

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