Enzyme Activity Changes as the Enzyme Concentration Decreases

Enzymes are a very important class of biocatalysts. Due to the action of the enzyme, the chemical reaction in the living body can be carried out efficiently and specifically under extremely mild conditions. The life processes of every creature on the earth, from small to large, proliferating, living and dying, and metabolism, are all related to enzymes. Without enzyme catalysis, the most basic food digestion, oxygen breathing cannot be carried out, let alone other life activities. In fact, almost all kinds of reactions occurring in living organisms are carried out by enzyme catalysis.

Enzymes are very important to life. The reason for this is that the rate of enzyme catalysis is very fast, which is thousands of times faster than the rate of reaction catalyzed by a chemical catalyst. For example, glucose in food reacts with oxygen to become carbon dioxide and water, and the energy released is the energy that maintains the body's body temperature and all life activities. If there is no catalyst, the catalytic process takes several years or longer under normal temperature and pressure conditions. To speed up the reaction, it must be carried out above three hundred degrees Celsius, burning and oxidizing to release energy. In the living body, under the catalysis of a series of enzymes, it can be completed instantaneously at normal temperature and pressure at an unimaginable speed.

Enzymes assist in chemical reactions by allowing molecules to reduce the energy required to initiate the reaction. This energy, called activation energy, is provided by the environment. For example, ambient thermal energy associated with ambient temperature can be used as activation energy. The rate of chemical reactions in a biological environment is usually limited by a limited amount of environmental energy, but enzymes overcome this limitation because they enable a smaller amount of energy to activate more reactions.

In most cases, reducing the enzyme concentration has a direct effect on the enzyme activity. An enzyme only catalyzes a reaction of one substance, or the same reaction of a chemically similar substance, and will never catalyze other substances and reactions. Most enzymes catalyze only one reaction of a substance, even if the structure is very similar. This property is called the specificity of enzyme catalysis. The enzyme-bound molecule is called a substrate. Typically, an enzyme is combined with a substrate to reduce the activation energy of a chemical reaction. If all of the enzymes in the system bind to the substrate, the additional substrate molecules must wait for the enzyme to become available after the reaction is complete. This means that as the enzyme concentration decreases, the reaction rate will decrease.

In most biological environments, the concentration of the enzyme is lower than the concentration of the substrate. The relationship between enzyme concentration and enzyme activity is directly proportional. On a graph showing reaction rate versus enzyme concentration, this direct proportional relationship looks like a straight line with a slope of one. In other words, one additional enzyme increases the rate by one reaction per unit time, and one removed enzyme reduces the rate by one reaction per unit time. An exception to the direct proportional relationship is that if the substrate concentration is below the enzyme concentration, lowering the enzyme concentration does not result in a decrease in enzyme activity. In this case, the removed enzyme has no effect because the system still has enough enzyme to bind to all available substrates. Thus, as the enzyme concentration increases to a level similar to the substrate concentration, the map of enzyme activity versus enzyme concentration will eventually settle to a flat line.