Diastase

Diastase is a general term for enzymes that hydrolyze starch and glycogen. Usually, diastase catalyzes the hydrolysis of starch pulp on fabrics. Due to the high efficiency and specificity of diastase, the desizing rate of enzyme desizing is high and the desizing is fast. Less pollution, the product is softer than acid method and alkali method, and does not damage the fiber. There are many types of diastases. According to different fabrics, different equipment combinations, and different process flows, the current desizing methods used are dipping, stacking, roll dyeing, continuous washing, etc. Due to the small mechanical effect of diastase desizing, the small amount of water can achieve desizing effect under low temperature conditions, and has distinct environmental protection characteristics.

Figure 1. Protein structure of Diastase

Classifications

Alpha-diastase is widely distributed in animals (saliva, pancreas, etc.), plants (malt, cornflower) and microorganisms. Microbial enzymes are almost all secretory. This enzyme takes Ca²⁺ as an essential factor and serves as a stabilizing factor and an activating factor, and some diastases are not Ca²⁺ dependent. The wide distribution of β-diastase differs from α-diastase in that the α-1,4-glucan chain is cut from the non-reducing end in units of maltose. It is mainly found in higher plants (barley, wheat, sweet potato, soybean, etc.), but it has also been reported in bacteria, milk, and mold. For the unbranched substrate like amylose, it can be completely decomposed to obtain maltose and a small amount of glucose. When acting on amylopectin or dextran, the reaction is stopped before the α-1,6-bond is cut, so a limit dextrin with a relatively large molecular weight is generated. γ-diastase is an exozyme, which sequentially cuts α(1→4) chain glycosidic bonds and α(1→6) chain glycosidic bonds from the non-reducing end of the starch molecule, cutting glucose residues one by one, similar to β-diastase The free hemiacetal hydroxyl produced by hydrolysis undergoes translocation, releasing β-glucose. Whether acting on amylose or amylopectin, the final product is glucose

Clinical significance

Increase

Found in pancreatic duct obstruction caused by pancreatic tumors, pancreatic abscess, pancreatic injury, intestinal obstruction, gastric ulcer perforation, mumps, peritonitis, biliary tract disease, acute appendicitis, cholecystitis, peptic ulcer perforation, renal failure or renal insufficiency , Salpingitis, traumatic shock, after major surgery, pneumonia, lung cancer, acute alcoholism, morphine injection, and oral contraceptives, sulfonamides, thiazide diuretics, opioids (codeine, morphine). Anesthesia and analgesics.

Reduce

Found in cirrhosis, hepatitis, liver cancer, acute or chronic cholecystitis, etc.

Pancreatic diastase is discharged from the pancreas into the digestive tract in an active state. It is the most important carbohydrate-hydrolyzing enzyme. Like diastase secreted by the salivary glands, it belongs to α-diastase and acts on α-1,4 glycosidic bonds. The α-1,6 glycosidic bond has no effect, so it is also called endodiastase. Its optimal pH is 6.9, which can be filtered through the glomerulus. It is the only plasma enzyme that can appear in urine in normal times.

Elevated serum diastase

Mostly seen in acute pancreatitis, it is one of the important diagnostic indicators of acute pancreatitis. Activity begins to increase 6 to 12 hours after onset, peaks at 24 hours, begins to decrease at 48 hours, and returns to normal after 3 to 5 days. Although the degree of increase in diastase activity is not necessarily related to the degree of pancreatic injury, the greater the degree of increase, the greater the possibility of acute pancreatitis, so although diastase is still used for diagnosis of acute pancreatitis The index is preferred, but its specificity and sensitivity are not high enough. When acute pancreatitis is suspected, the patient's serum and urine diastase activities should be continuously and dynamically observed, and combined with clinical conditions and other tests, such as pancreatic lipase, trypsin and other measurements, to make a diagnosis.

Reference

1. Ramasubbu N.; et al. Structure of human salivary alpha-amylase at 1.6 Å resolution: implications for its role in the oral cavity. Acta Crystallographica D. 1996, 52 (3): 435-446.