English name: amylase

Definition: An enzyme that can hydrolyze O- glucose bonds in starch, glycogen and related polysaccharides.

Applied disciplines: biochemistry and molecular biology (first-class disciplines); Enzymes (two disciplines)

Amylase is a general term for enzymes that hydrolyze starch and glycogen. Usually, the starch slurry on the fabric is hydrolyzed by amylase. Because of the high efficiency and specificity of amylase, enzyme desizing has high desizing rate, rapid desizing and less pollution. This product is softer than acid method and alkali method, and does not damage the fiber. There are many kinds of amylases. According to different fabrics, different equipment combinations and different technological processes, the desizing methods currently used include dipping method, stacking method, jigging method and continuous water washing. Because the mechanical effect of amylase desizing is small and the water consumption is small, it can achieve desizing effect at low temperature, which has distinct environmental protection characteristics.

Starch saccharifying enzyme

Amylase, Amy and AMS generally act on α- 1, 4- glucan such as soluble starch, amylose and glycogen to hydrolyze α- 1, 4- glycoside bond. According to the different isomeric types of enzymatic hydrolysate, it can be divided into α -amylase (EC3.2. 1. 1 .+0.) and β -amylase (EC 3.2. 1.2). ).

α -amylase is widely distributed.

In animals (saliva, pancreas, etc. ), plants (malt, turnip) and microorganisms. Almost all microbial enzymes are secreted. This enzyme takes Ca2+ as essential factor, as stabilizing factor and activating factor, and some amylases are independent of Ca2+. Amylase acts on amylose and amylopectin at the same time, and randomly cuts off the α- 1, 4- chain inside the sugar chain indiscriminately. Therefore, the viscosity of the substrate solution drops sharply and the iodine reaction disappears. In addition, when amylose is decomposed, there are a small amount of maltotriose and maltose in the final product. Among them, the final product of fungal α -amylase hydrolysis of starch is mainly maltose, which is widely used in baking industry and maltose manufacturing industry. On the other hand, when amylopectin is decomposed, besides maltose, glucose and maltotriose, α- 1, 6- bonded α-limit dextrin (also called α-dextrin) is also produced. Generally, based on glucose, the decomposition limit is 35-50%, but in bacterial amylase, it is as high as 70% (glucose finally dissociates);

β -amylase is widely distributed.

Unlike α-amylase, α- 1, 4- glucan chain is cut off from the non-reducing end in maltose unit. It mainly exists in higher plants (barley, wheat, sweet potato, soybean, etc.). ), but it has also been reported in bacteria, milk and mold. Maltose and a small amount of glucose can be completely decomposed as an unbranched substrate like amylose. When it acts on amylopectin or dextran, it is cut into α- 1, 6- bond, and the previous reaction stops, thus producing limit dextrin with relatively large molecular weight. According to the action modes of α -amylase and β -amylase mentioned above, α- 1, 4- glucan -4- glucohydrolase (α- 1, 4- glucan hydrolase) and α- 1, 4- glucan-maltose hydrolase (α-65438) were proposed respectively.

γ -amylase

Glucoamylase, glucoamylase, No.E.C.3.2.1.3 γ-amylase (γ-amylase) is a nucleic acid exonuclease, which cuts off the α( 1→4) chain glycosidic bond and α( 1→6) from the non-reducing end of starch molecules in turn. Whether it acts on amylose or amylopectin, the final product is glucose. [ 1]

isoamylase

Starch-1, 6- glucosidase, code E.C.3.2. 1.33 All animals, plants and microorganisms produce isoamylases. Different sources have different names, such as debranching enzyme, Q enzyme, R enzyme, pullulanase, pullulanase and so on. Hydrolyze α- 1, 6- glycosidic bond of amylopectin or glycogen to produce amylose (dextrin) with different lengths. It is mainly produced by microbial fermentation, and the strains are yeast, bacteria and actinomycetes.

Clinical significance of editing this paragraph

heighten

It can be seen in pancreatic duct obstruction, pancreatic abscess, pancreatic injury, intestinal obstruction, gastric ulcer perforation, mumps, peritonitis, biliary tract diseases, acute appendicitis, cholecystitis, peptic ulcer perforation, renal failure or renal insufficiency, salpingitis, traumatic shock, postoperative pneumonia, lung cancer, acute alcoholism, morphine injection, oral contraceptives, sulfonamides, thiazide diuretics and so on. Anesthetic analgesics, etc.

decrease

It is found in liver cirrhosis, hepatitis, liver cancer, acute and chronic cholecystitis, etc.

Pancreatic amylase is discharged into the digestive tract by the pancreas in an active state and is the most important enzyme for hydrolyzing carbohydrates. Pancreatic amylase, like amylase secreted by salivary gland, belongs to α-amylase, which acts on α- 1 4 glycosidic bond, but has no effect on α- 1 6 glycosidic bond on the branch, so it is also called endoamylase. Its optimum pH value is 6.9, and it can be filtered through the glomerulus.

Amylase activity is found in the extracts of other tissues of human body, such as ovary, fallopian tube, lung, testis, semen and mammary gland. Amylase is also found in blood, urine and emulsion. Blood amylase mainly comes from pancreas and salivary glands, while urine amylase comes from blood.

In the determination of serum amylase isoenzymes, two main isozyme bands and several secondary bands were found. One of the two main bands is called P- isoenzyme because it has the same electrophoretic position as the purified or secreted products of pancreas. The other is named S isozyme because it has the same position as salivary gland extract or saliva electrophoresis. The determination of amylase isoenzymes is helpful for the differential diagnosis of pancreatic diseases.

Reference value:

Restrictive substrate method: serum amylase 220U/L(37℃), urine amylase 1200U/L(37℃), P isoenzyme serum1kloc-0/5 u/l, urine 800U/L, and neonatal serum amylase is about/kloc-0 of adults. Serum P- amylase was not detected at the age of one year, and then slowly increased, reaching the human level at the age of 10 ~ 15.

The determination of serum amylase and urine amylase is the most commonly used diagnostic method for pancreatic diseases, which can increase or decrease the activity of pancreatic diseases or pancreatic exocrine dysfunction and contribute to the diagnosis of pancreatic diseases. Urinary amylase level fluctuates greatly, so it is best to detect it with serum amylase or both. Changes in amylase activity can also be seen in some non-pancreatic diseases, and it is of differential diagnostic significance to determine amylase isoenzymes when necessary.

Elevated serum amylase

It is the most common in acute pancreatitis and one of the important diagnostic indexes of acute pancreatitis. At 6 ~12 hours after onset, the activity began to increase, peaked at 24 hours, began to decrease at 48 hours and returned to normal at 3 ~ 5d days. Although the increase of amylase activity is not necessarily related to the degree of pancreatic injury, the greater the increase, the greater the possibility of acute pancreatitis. Therefore, although amylase is still the first choice to diagnose acute pancreatitis, its specificity and sensitivity are not high enough. When acute pancreatitis is suspected, the patient's serum and urine amylase activities should be continuously and dynamically observed, and the diagnosis can be made in combination with clinical conditions and other tests, such as the determination of pancreatic lipase and trypsin.

Amylase determination is also valuable for monitoring complications of acute pancreatitis, such as pancreatic pseudocyst and pancreatic abscess. At this time, the amylase activity in the blood continues to increase. Severe acute pancreatitis can cause pleural effusion or/and peritoneal effusion, and the amylase activity in the effusion can even be 0/00 times higher than that in serum/kloc.

The diagnosis of acute pancreatitis is difficult, because other acute abdomen can also cause the increase of amylase activity. Therefore, when acute pancreatitis is suspected, besides continuous monitoring of amylase, the diagnosis should be made in combination with clinical conditions and other tests, such as pancreatic lipase and trypsin.

Amylase activity can be slightly increased or decreased in chronic pancreatitis, but it has no great diagnostic significance. Amylase activity increased in early stage of pancreatic cancer.

Moderate or slight increase in amylase activity can also be seen in some non-pancreatic diseases collected by Medical Education Network, such as mumps, acute abdomen (peptic ulcer perforation, upper abdominal surgery, mechanical intestinal obstruction, mesenteric vascular disease, biliary obstruction, acute cholecystitis, etc. ), taking analgesics, alcoholism, renal insufficiency and macroamylasemia. This should be noted.

Amylase in blood can be filtered by glomerulus, so when serum amylase rises for any reason, it will increase the excretion of amylase in urine, especially acute pancreatitis. In acute pancreatitis, the ability of kidney to clear amylase is enhanced, which can increase earlier than blood amylase and decrease later than blood amylase.

Amylase isozyme

Serum amylase not only comes from pancreas, but also from salivary glands and other tissues, so when amylase activity increases, the determination of isoenzymes is helpful for differential diagnosis of diseases. When P- isoenzyme increases or decreases, it may indicate pancreatic diseases. The changes of S- isoenzyme may originate from salivary glands or other tissues. When the serum amylase activity increases and the diagnosis is unclear, isoenzymes should be further determined to help differential diagnosis. There are many methods to determine isoenzymes, and agarose and cellulose acetate membrane electrophoresis are commonly used.

The determination results of amylase are greatly influenced by methods, and the reference values of different methods are different, so there are many methods used in clinic. Therefore, it is necessary to know the determination method and its reference value before making a correct diagnosis.

Amylase causes dry lips.

In order to moisten lips, some people like to lick their lips with their tongues. In fact, this is a bad habit, because licking your lips can only bring temporary wetness. When the water in these lips evaporates, it will take away more water inside the lips, so that your lips will fall into a vicious circle of "dry-lick-dry-lick again", and the result will be more painful and cracked. At the same time, saliva contains amylase and other substances. When the wind blows, the water evaporates and takes away the heat, which lowers the temperature of the lips. Amylase sticks to the lips, which will cause the deep connective tissue to contract and wrinkle the lip mucosa, thus drying more severely. In severe cases, it will be infected and swollen, causing pain.