Now let us consider the general principles of digestion that are applicable t6all animals. We will start with the digestive enzymes that breakdown the large food molecules into smaller soluble component units. This breakdown involves the uptake of water and is called hydrolysis. However, digestive enzymes differ in the following ways:
a) Digestive enzymes are not as narrowly specific as other enzymes rather they show group specificity. For example, enzymes that digest carbohydrates can digest polysaccharides of both animal and plant origin,
b) Even though enzymes performing similar functions in different animals are given same names, they are not identical chemically. For example, trypsin (an enzyme, that hydrolyses proteins) in humans is not identical to that found in fish. Temperature and pH for optimum activity is also different. For example, trypsin from vertebrate pancreas acts best in the pH range of 7-9 but in silkworm the pH range is 6.2-9.
c) Digestive enzymes from pancreas particularly those that digest proteins are secreted in an inactive form.
The three major classes of digestive enzymes are: