The role of general digestive enzymes is hydrolysis. Some digestive enzymes are secreted by digestive glands, and some participate in intracellular digestion.Extracellular digestionAmong the enzymes, there arePepsinogen、Trypsinogen、ProcarboxypeptidaseIt is secreted in the form of inactive proenzyme and then activated.[1]
digestive enzyme
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(1) Proteolytic enzyme (protease):PepsinIn addition to being present in the gastric juice of higher animals, protease also has the same property in invertebrates.But many of its characters are still unknown.Trypsin exists in pancreatic juice of higher animals.In lower animals（Crustacea, dipods, etc.) also exist in active state.But it is not clear whether it is the same as higher animals.Chymotrypsin is contained in the pancreatic juice of higher animals, and aminopeptidase is contained in the intestinal juice of higher animals. In addition to acting as the intermediate decomposition product of proteinMidgut glandIt is secreted as gastric juice and also exists as digestive enzyme in the cells of midgut gland.Carboxypeptidase exists in the midgut gland of lower animals in activated form, except in the pancreatic juice of higher animals.Aminophthalein proline (dipeptidase) enzyme, proline amino acid (dipeptidase), dipeptidase, leucineAcyl peptideEnzymes exist in the intestinal fluid of higher animals.Protamine exists in the pancreatic juice of higher animals,KeratinaseIt is a special digestive enzyme existing in the intestinal juice of cuttlefish.Rennin (crude rennin) exists in the gastric juice of higher animals.Enterokinase is secreted by the duodenal epithelium of higher animals.Cathepsin is generally believed to exist in the gastric juice of higher animals and also in the midgut of lower animals. It is originally a proteolytic enzyme in cell tissue, so it does not directly participate in digestion.
(2) Carbohydrate decomposing enzyme;α-Glucosidase(Maltase) is found in saliva, intestinal juice of higher animals and digestive juice of lower animals.β - glucosidase exists in the small intestine fluid of higher animals.β - galactosidase (lactase) exists in the intestinal juice of higher animals and the digestive juice of lower animals.Amylase is widely found in saliva, pancreatic juice of higher animals and digestive juice of lower animals.Amylase in saliva of higher animals is specially called salivary amylase.Cellulase exists in the digestive juice of lower animals, in the saliva of the woodworm moth, in the midgut cells (intracellular digestion) of the scallop, in the intestinal juice of some wood piercing insect larvae and other parts. In addition, parasites (bacteria, protozoa, etc.) in the digestive tract of higher animals (including some lower animals) also secrete.Lignase and chitinase are present in the midgut gland secretion (gastric juice) of snails.Inulinase(inulase) exists in the midgut secretion of snails and the cells of the digestive blind sac of oysters (intracellular digestion).Xylanase exists in the intestinal juice of sheep, horses, etc., and even in the midgut gland of snails (Cellana) abalone, etc. It is unclear whether the former is derived from parasitic bacteria, and whether the latter is directly involved in intracellular digestion.ArgininaseIt is found in the digestive juice of Calotomus japonicus, abalone, Rongluo, etc.
(3) Adipolytic enzyme: lipase, which exists in the pancreatic juice of higher animals, and also in the deformed cells (digestive syncytium) of stomach, midgut gland and lower animals.
（4）RibonucleaseDeoxyribonuclease was found in pancreatic juice of higher animals.Nucleosidase, found in the intestinal fluid of higher animals.
The digestive function of the human body depends on gastrointestinal movementMechanical digestionAnd digestive enzymes.Digestive juice contains a lot of digestive enzymes, which can promote the hydrolysis of sugar, fat and protein in food.It changes from macromolecular substances to small molecular substances so as to be absorbed and utilized by the human body.Glucose, glycerin, glycerol ester, amino acid, etc. are small molecules that can be dissolved and absorbed by the small intestine.In clinical practice, insufficient digestive enzymes can not only cause a wide range of dyspepsia symptoms, such as gastrointestinal flatulence, stomach fullness, nausea, abdominal pain, diarrhea, anorexia and other symptoms, but also affect the digestion and absorption of nutrients, resulting in hypoproteinemia, fatty diarrhea, lack of fat soluble vitamins, endocrine disorders and so on.The main causes of digestive enzyme deficiency are: chronic pancreatitis, cholelithiasis, liver cirrhosis, liver dysfunction, pancreatic cancer, chronic gastrointestinal diseases, after pancreatectomy, gastrectomy, cholecystectomy, side effects of radiotherapy or chemotherapy, senile digestive dysfunction, and long-term drinking.The mechanism of dyspepsia is very complex, and the insufficient secretion of digestive enzymes or decreased function is an important part of dyspepsia
Summary of characteristics of digestive enzymes
Digestive enzyme is the substance contained in the digestive juice secreted by human digestive organs, which is a kind of protein.
The main function of digestive enzymes is to decompose food into small molecules that can be absorbed by the human body.
All enzymes are specific. One kind of enzyme only catalyzes another or a kind of chemical reaction, so there are many kinds of digestive enzymes.
Digestive enzyme has biological activity, which is greatly affected by external environment (temperature, humidity,PH）Etc.
