What is the function of digestive enzymes?

When talking about digestion, we have to mention our stomach. No matter what food it is, even if it is not edible, it can generally be digested and the waste can be excreted from the body with the help of the intestines. So, what substance does the stomach rely on to digest food? In fact, this is inseparable from the help of digestive enzymes. Digestive enzymes are substances secreted by digestive glands. Let's take a look at their main functions.

Digestive enzymes

Digestive enzyme: A general term for enzymes involved in digestion. Generally, the function of digestive enzymes is hydrolysis. Some digestive enzymes are secreted by digestive glands, while others are involved in intracellular digestion. Among the extracellular digestive enzymes, some are secreted in the form of inactivated zymogens such as pepsinogen, trypsinogen, and carboxypeptidase and then activated. Lack of digestive enzymes can lead to incomplete breakdown of food, which then accumulates in the colon, creating an environment prone to indigestion, degenerative diseases, and rapid aging.

Types

Protease

Pepsin, in addition to existing in the gastric juice of higher animals, is also a protease with the same properties in invertebrates. However, many of its properties are still unclear. Trypsin, present in the pancreatic juice of higher animals. It also exists in an active state in the gastric juice of lower animals (crustaceans, gastropods, etc.). But whether it is the same as in higher animals is not clear. Chymotrypsin is contained in the pancreatic juice of higher animals, and aminopeptidase is present in the intestinal juice of higher animals. In addition to acting on the intermediate decomposition products of protein, it is secreted as gastric juice in the midgut glands of snails and murex of lower animals, and also exists as a digestive enzyme in the midgut gland cells. In addition to the pancreatic juice of higher animals, carboxypeptidase exists in an activated form in the midgut glands of lower animals. Proline (dipeptidase), proline amino acid (dipeptidase), dipeptidase, and leucyl peptidase are present in the intestinal fluid of higher animals. Protase is present in the pancreatic juice of higher animals, and keratinase is a special digestive enzyme present in the intestinal juice of squid. Rennin (crude rennin) exists in the gastric juice of higher animals. Enterokinase is secreted by the duodenal epithelium of higher animals. Tissue proteases are generally believed to exist in the gastric juice of higher animals and in the midgut of lower animals. Originally, since they are proteolytic enzymes within cell tissues, they are not directly involved in digestion.

Degradation enzyme

α-Glucosidase (maltase) exists in the saliva and intestinal fluid of higher animals and even the digestive fluid of lower animals. β-glucosidase, present in the small intestinal fluid of higher animals. β-galactosidase (lactase) exists in the intestinal fluid of higher animals and the digestive fluid of lower animals. Amylase is widely present in the saliva and pancreatic juice of higher animals and the digestive juices of lower animals. The amylase in the saliva of higher animals is specifically called salivary amylase. Cellulase is present in the digestive fluids of lower animals, the saliva of wood borers, the midgut cells of shipshells (intracellular digestion), the intestinal fluid of certain wood-boring insect larvae and other parts. In addition, it is also secreted by parasites (bacteria, protozoa, etc.) in the digestive tract of higher animals (including some lower animals). Ligninase and chitinase are present in the midgut gland secretions (gastric juice) of snails. Inulase is present in the midgut secretions of snails and in the cells of the digestive caeca of oysters (intracellular digestion). Xylanase is present in the intestinal fluid of sheep and horses, as well as in the midgut glands of snails (Cellana) and abalone. It is not clear whether the former comes from parasitic bacteria, and whether the latter is directly involved in intracellular digestion is also unclear. Arginase is present in the digestive juices of Calotomus japonicus, abalone, and snails that feed on laminarin plants.