An enzymatic reaction refers to a chemical reaction catalyzed by an enzyme as a catalyst. Factors that affect enzymatic reactions are temperature, pH, enzyme concentration, substrate concentration, inhibitors and activators. Understanding the chemical nature of enzyme preparations is of great significance for the rational and correct use of enzyme preparations. This article briefly introduces several factors that affect the catalytic effect of enzyme preparations.
pH Each enzyme only exhibits high activity in a specific pH range, which is the optimum pH for enzyme action. Generally, enzymes are most stable at pH optimum. If the pH value of the enzyme reaction is too high or too low, the enzyme will be irreversibly damaged, and its stability, activity will decrease, or even inactivation. The optimum pH range of different types of enzymes is different, and there are some acidic, neutral and alkaline. For example, according to the optimal pH value of protease, it is often divided into acidic protease, neutral protease and alkaline protease. The optimum pH of the enzyme is different depending on the temperature or substrate. The higher the temperature, the narrower the stable pH range of the enzyme. Therefore, in the process of enzyme-catalyzed reaction, the pH value of the reaction must be strictly controlled.
Temperature Under certain conditions, each enzyme has an optimum temperature. At this temperature, the enzyme activity is the highest, the effect is the best, and the enzyme is relatively stable. The speed of the enzyme-catalyzed reaction increases and the thermal denaturation loss of the enzyme activity reaches a balance, and this temperature is the optimum temperature for the enzyme action.
Each enzyme has a temperature at which its activity is stable. At this temperature, under a certain time, pH and enzyme concentration, the enzyme is relatively stable, and the activity is rarely decreased. This temperature is the stable temperature of the enzyme. However, the enzyme is rapidly inactivated by acting above the steady temperature. This thermal sensitivity of the enzyme can be expressed by the critical failure temperature Tc, which refers to the temperature at which the enzyme loses half of its activity in 1 hour. Therefore, generally only within the effective temperature range of the enzyme, can the effective catalysis be carried out. For every 10 °C increase in temperature, the enzyme reaction speed increases by 1 to 2 times.
Enzyme Concentration and Substrate Concentration Substrate concentration is the main factor that determines the rate of enzyme-catalyzed reaction. When the substrate concentration is extremely low, the catalytic reaction rate of the enzyme increases rapidly with the increase of the substrate concentration, and the two are proportional. As the substrate concentration increased, the reaction rate slowed down and no longer increased proportionally. Sometimes the substrate concentration is very high, and the enzyme reaction speed is also reduced due to substrate inhibition. When the substrate concentration greatly exceeds the enzyme concentration, the enzyme-catalyzed reaction rate is generally proportional to the enzyme concentration. Also, if the enzyme concentration is too low, the enzyme sometimes fails, preventing the reaction from proceeding. For the enzyme-catalyzed reaction in food processing, the amount of enzyme is generally much less than that of the substrate, and the cost of the enzyme should also be considered.
Inhibitors Many substances can weaken, inhibit, or even destroy the action of enzymes. These substances are called enzyme inhibitors. Such as heavy metal ions (Fe3+, Cu2+, Hg+, Pb+, etc.), carbon monoxide, hydrogen sulfide, organic cations, ethylenediamine and tetraacetic acid, etc.