All digestive fluid of the human body contain enzymes that degrade food into simple soluble substances. These substances called digestive enzymes can be divided into three types: amylase, protease and lipase.

Amylase promotes the degradation of carbohydrates, and the most complex carbohydrate is a polysaccharide. Each polysaccharide is composed of monosaccharide molecular chains, and most of the carbohydrates absorbed by the human body are polysaccharides, such as starch and glycogen. Starch is a plant-derived polysaccharide, glycogen or animal starch, a complex polysaccharide stored in animal liver or muscle. In the degradation of polysaccharides, the compounds sucrose and lactose composed of two monosaccharide molecules in the intermediate state are first formed. Sucrose is found in sugar beets and sugar cane, and lactose is found in milk. Monosaccharides are the simplest sugars, all due to the degradation of polysaccharides. Although some of the fructose absorbed by the body comes from fruit juice, some come from the degradation of sucrose. Glucose is the final result of all sugars, and both fructose and galactose are converted into glucose in the liver.

Proteases attack peptide bonds and promote the degradation of proteins into amino acids. Most protein molecules contain hundreds of amino acids, which are connected by substances called peptide bonds, called peptides. The dipeptide is a chain formed by two amino acid molecules and is an intermediate state formed by the degradation of a polypeptide.

The digestive system is the oral cavity first, its digestive juice is saliva, and the digestive enzyme is salivary amylase, which degrades the starch and glycogen of sugars to produce a shorter polysaccharide-dextrin.

Then the food enters the stomach. The digestive juice in the stomach is gastric juice, which is produced by the gastric glands of the gastric mucosa and secreted into the stomach. Digestive juice includes digestive enzymes and other components, including pepsin, hypertensive proteinogenase (existing only in young people), hydrochloric acid, and gastric lipase (mainly present in young people).

The role of gastric digestive juice is as follows: pepsin starts to degrade proteins (polypeptides). The hypertensive proteinogen enzyme interacts with calcium to form a viscous milky, that is, it interacts with protein (casein). Hydrochloric acid activates pepsin, which becomes thick and milky in adults and kills bacteria. Stomach lipase starts to degrade fat molecules in milk. The result is the formation of shorter peptide bonds, viscous milky solids and intermediate compounds.

Pancreatic juice is produced by the pancreas and secreted into the duodenum in the small intestine. Its digestive enzymes are trypsin, chymotrypsin, carboxypeptidase, pancreatic amylase, and pancrelipase. The first three enzymes continuously degrade proteins, from long peptides to short peptides. Pancreatic amylase continuously degrades sugars. Pancrelipase degrades fat into particles. The resulting products are dipeptides and certain amino acids, maltose (disaccharides), glycerol and fatty acids.

Bile is produced by the liver stored in the gallbladder and secreted into the duodenum in the small intestine. Its components are bile salts and bile acid. Break down fat (and intermediate compounds) into smaller particles, this process is called emulsification.

Intestinal juice is produced by intestinal glands in the lining of the small intestine. Eventually secreted into the small intestine. Its digestive enzymes include maltase, sucrase, lactase, and intestinal juice promoting hormone. They function to degrade maltose, degrade sucrose, degrade lactose, and complete protein degradation. The resulting products are glucose or dextrose, glucose and fructose, glucose and galactose, and amino acids.

The small intestine is the main place to absorb nutrients. All glucose, amino acids, glycerol, fatty acids and part of water, inorganic salts and vitamins are absorbed in the small intestine. After the blood flows into the wall of the small intestine, due to physiological activities, oxygen decreases and the absorbed nutrients increase to supply nutrients to the various organs of the body.

We are very familiar with amylase, no matter in biochemistry, biochemical inspection, or internal medicine, we cannot avoid amylase. Amylase testing is also one of the most commonly used testing items in clinical laboratories.

The discovery of amylase can be traced back to the first development stage of biochemistry. In 1833, Payen, who worked in a sugar factory, separated a soluble substance from malt that could convert starch into sugar and called it amylase. In 1878, Cunai first proposed the concept of “enzyme” based on previous chemical research. Amylase became the first enzyme discovered in the history of enzymology.

What is amylase

Amylase is an exocrine hydrolase that is mainly derived from pancreatic synthesis, mainly in the digestive tract, and can hydrolyze α-1,4 glycosidic bonds. Of course, there is not only amylase that can hydrolyze glycosidic bonds in the body, but also phosphorylase that hydrolyzes α-1,4 glycosidic bonds in the process of glycogen decomposition, which has the bidirectional function of forming and decomposing α-1,4 glycosidic bonds. Branch chain transferase, α-1,6 glycosidase that hydrolyzes α-1,6 glycosidic bonds; amylase that enters the blood rarely exerts catalytic activity.

The source of amylase

There are two main isoenzymes of amylase in the body, one is pancreatic amylase: mainly synthesized by pancreas and testicular cells, the pancreas is the main organ for synthesizing amylase; the other is salivary amylase: mainly from the salivary glands and also found in lungs, ovaries and other tissues.

What can the source distribution of amylase show? (1) The occurrence of diseases in these tissues will cause the increase of serum amylase; (2) The pancreas is the main organ for the synthesis of amylase, so the diseases of the tissues and organs around the pancreas can also affect the pancreas and cause the increase of serum amylase.

The nature of amylase

In enzymology, amylase is a metalloenzyme, or calcium ion metalloenase to be precise. This property of amylase determines: (1) In pathophysiology, calcium ion levels are inextricably linked with amylase and acute pancreatitis; (2) In clinical tests, amylase test samples meet following requirements, that is, the usual sodium citrate, EDTA, and even heparin (although the main anticoagulation mechanism of heparin is not to chelate calcium ions, heparin also has calcium binding sites) and other anticoagulant specimens that bind calcium ions. It is not advisable to detect amylase. In terms of molecular weight, the molecular weight of amylase is about 45kd. The molecular weight of 45kd indicates that amylase is a medium-molecular-weight protein, so amylase can be partially filtered out through the glomerular filtration membrane and appears in the urine. It also indicates that the kidney’s filtration capacity will affect the level of urine amylase and reduce the glomerulus diseases of filtration capacity may cause a slight increase in blood amylase.

Blood amylase and pancreatitis

Amylase is used for the auxiliary diagnosis and differential diagnosis of clinical pancreatitis. To be precise, it is used for the clinical diagnosis of acute pancreatitis and the clinical diagnosis of acute episodes of chronic pancreatitis, especially edematous acute pancreatitis. It has no diagnostic effect on general chronic pancreatitis. Necrotizing pancreatitis can have normal or decreased amylase levels.

Urine amylase and pancreatitis

In acute pancreatitis, urine amylase rises late, starting to rise after 12-14 hours; but it lasts for a long time, lasting 7-14 days. It can be seen that compared with blood amylase, not only amylase can be present in urine, but the duration of amylase in urine is longer, the detection window is longer, and the reference interval is wide.

(1) The molecular weight of amylase is small

As mentioned above, the molecular weight of amylase is only about 45kd, indicating that amylase can be partially filtered out through the glomerular filtration membrane.

(2) Renal tubules partially reabsorb amylase

Whether amylase appears in the final urine also depends on the kidney’s reabsorption and secretion mechanisms. Do these mechanisms have an effect on urine amylase? The renal tubules have partial reabsorption capacity for amylase.

(3) The priority filtering mechanism of the kidney

Mere filtration and partial reabsorption are not enough to explain the long duration of urine amylase and the long detection window. The kidney also has a preferential filtering mechanism for blood amylase, that is, the kidney can preferentially filter amylase, and the higher the blood amylase, the stronger the kidney’s filtering ability. The preferential filtration mechanism allows urine amylase to show higher levels in a relatively regular period of time after the blood amylase begins to decrease.

(4) The urine concentration and dilution mechanism of the kidney

The body interacts with the kidneys through the action of antidiuretic hormone, and uses the different transmembrane transport mechanisms of NaCl and urea in different sections of the renal tubular collecting duct to realize the concentration and dilution of urine. The urine concentration and dilution mechanism undoubtedly caused the urine amylase to present a wider reference interval in the normal population, and thus did not have better diagnostic sensitivity.

As people pay more and more attention to food safety, nutrition, health and deliciousness, food is not only to meet people’s basic needs for survival, but the food industry is developing in a safer, more nutritious and delicious direction. Therefore, enzyme, as a high-efficiency biocatalyst, is replacing traditional chemical agents with its unique advantages, and is being used more and more widely in the food industry. The enzyme industry has become one of the most promising emerging industries in our country.

Cellulase is a general term for a group of enzymes that can hydrolyze cellulose into glucose. The source of cellulase is very wide. In addition to fungi, various protozoa, roundworms, mollusks, earthworms, crustaceans, insects, algae, fungi, bacteria and actinomycetes can produce cellulase.

Application of cellulase

1) Soy sauce brewing

Soy sauce is a hydrolysate of soybean protease. Soy sauce brewing mainly uses enzymes such as protease and amylase to hydrolyze raw materials. If cellulase is used again, the cell membranes of raw materials such as soybeans can be expanded, softened, and destroyed, and the proteins and carbohydrates contained in the cells can be released. This can shorten the brewing time, increase the yield, improve the quality of the product, and increase the amino acid reducing sugar content of the product.

2) Beer production

In the beer production process, the use of cellulase enzymes can convert starch and cellulose into sugar, which are then completely converted into alcohol by yeast decomposition. The wine yield can be increased by 3% to 5%, and the utilization rate of starch and cellulose can be as high as 90%. Using cellulase to hydrolyze brewer’s grains, and effectively utilize the enzymatic hydrolysate and residues separately, can greatly improve the economic and environmental benefits of brewer’s grains.

3) Fruit and vegetable processing

In the process of fruit and vegetable processing, in order to soften plant tissues, methods such as heating and cooking, acid and alkali treatment are generally used, which will cause loss of flavor and vitamins. Treatment of fruits and vegetables with cellulase can avoid the above-mentioned shortcomings, and at the same time can make plant tissues soft and bulky, thereby improving their digestibility and improving taste.

4) Tea processing

The traditional production process of instant tea is to steep the tea leaves in boiling water to extract the effective ingredients in the tea cells, such as amino acids, sugar, caffeine, saponins, tea polyphenols, tea aroma components and pigments, etc., and then freeze-dry them at low temperature. If the tea is properly treated with cellulase, it can lower the temperature of immobilized enzyme production, shorten the extraction time, improve the taste of instant tea, and increase the yield.

5) Oil crop processing

Cellulase also plays a very important role in oil crop processing. Traditionally, the squeezing method or the organic solvent method has been used to produce oil products, which have poor product quality, low yield, long operating time, and organic solvent residues are inevitable. Using enzyme treatment method instead of organic solvent method can improve the output and quality of oil on the one hand. On the other hand, by controlling the enzyme reaction conditions, the production and processing can be carried out under milder conditions, which can avoid the impact of severe conditions on product quality. Therefore, the use of enzyme technology in the field of agricultural product processing can not only increase the yield of the main product, but also reduce the generation of by-products and reduce waste treatment costs.

Enzymes have been widely used in the food industry. It can be expected that with the rapid development of biotechnology itself, especially the application of genetic engineering technology, the types of enzyme preparations that can be used in food will greatly increase. On the one hand, people’s requirements for food varieties and quality are constantly increasing, and the application of enzyme preparations will make great progress. Among them, the use of enzyme preparations to produce functional foods with health benefits will be an important research field. On the other hand, people’s expectations for food safety are getting higher and higher, which brings new opportunities for the application of enzymatic technology in food testing, and new developments are expected in the future.