Peroxidase is a group of globular protein enzymes that play a vital role in multiple biological processes. The optimal substrate in such cases of enzymes is hydrogen peroxide (H2O2). The peroxidase enzyme converts the substrate hydrogen peroxide (H2O2) into products as water (H2O) and oxygen molecules (O2). It is the specific characteristic of enzymes that they speed up the biological process but are not consumed. Substrate attaches to the active site of the peroxidase enzyme and is converted into respective products. The reaction rate, in this case, is observed by decreasing the number of reactants and increasing the number of products. Various factors affect the reaction rate of the peroxidase enzyme, such as temperature, pH, substrate, and available amount of enzyme. The biological reaction increases with the increase of temperature and reaches an optimal position, which gradually slows down and eventually freezes. The optimal temperature in the case of the human body is 37 °C. Similarly, the amount of substrate affects the rate of reaction. Suppose the amount of hydrogen peroxide has increased, the rate of reaction increases, and vice versa. The same principle applies to the amount of enzyme. As far as the pH is concerned, its higher and lesser value, i.e., acidic and basic, denatures the enzyme. The rate of reaction becomes more elevated at the optimal pH value.
The activity of the peroxidase enzyme can be observed in two ways. The first one is the observation of gas bubbles that evolve during the reaction. However, the detection is not so practical and notable. The most appropriate and reliable way is the usage of an indicator, guaiacol. The said indicator reacts with the oxygen molecule (O2) and is transformed into tetraguaiacol, converting colorless water into brownish-colored. The color change commences with a slight shift in the full brown color of the water. In this way, the activity of the peroxidase enzyme can be detected.