Action of Pancreatic Amylase

Potato starch (800 g.) in 9 liters of water containing 2 g. of sodium chloride was hydrolyzed at 20° for twenty weeks with 1 g. of pancreatin (Pharm. Svec. Ed. X) (Table XXV). Apart from small amounts of higher saccharides, tetra- and trisaccharides predominate. The total yield of limit dextrins is high, possibly because the pancreatin contains lower amounts of dextrin-splitting enzymes or because its action ceases at a greater distance from the anomalies. 

The rate of hydrolysis of the dextrin fractions in mineral acid was determined. All fractions have a rate of hydrolysis lower than that of the starch and the reaction coefficient falls gradually. Surely this is due to the occurrence of the 1,6-D-glucosidic linkages. 

Fraction PPX (15.8 g.) of Table XXV was treated with 2.85 N sulfuric acid at 100° for one hour. As a result, 57 % of the D-glucosidic linkages were ruptured. Maltose and D-glucose were removed, and 5.2 g. of a sirupy disaccharide, fermented very slowly by bakers yeast, was recovered. The rate of hydrolysis of this disaccharide in acid was considerably slower than that of fraction PPX hence, the isomaltose linkages have been concentrated during the first hydrolysis. 

Limit Dextrins from Barley Starch with Taka-amylase 

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Each salt was present in the concentration and at the hydrogen ion activity which had been found to be most favorable to the action of pancreatic amylase in the presence of that salt. 

The slowing down of enzyme reactions has often been attributed to reaction with, or equilibrium between, the enzyme and its substrate or between the enzyme and the products of its action. In order to determine the influence of the products of the action of pancreatic amylase on the extent of the hydrolysis of starch, portions of its hydrolysis mixtures were subjected to efficient dialysis during hydrolysis and the results compared with aliquots of the reaction mixture which had been treated in the same way except for dialysis.41 The results of such experiments... 

Carbohydrates, or starches, which are complex polysaccharides, are hydrolyzed to oligosaccharides and disaccharides by the action of pancreatic amylase. Disaccharides, including lactase, sucrase, and maltase, are enzymatically split by enzymes contained in the microvilli of enterocytes. Glucose and other monosaccharides are absorbed by an active transport mechanism and this action is coupled to energy derived from a sodium pump mechanism. 

Ans. Although starch digestion begins in the mouth with the action of salivary amylase, only a small portion of dietary starch digestion is completed there. The bulk of the starch digestion occurs in the small intestine under the action of pancreatic amylase. 

An interesting comparison is also given in Table XI86 of the action of malted barley alpha amylase upon corn starch, beta dextrins obtained from corn starch by the action of beta amylase, and upon corn amylose prepared according to the method of Meyer.6 90 These data show that, with equivalent amounts of enzyme, amylose was hydrolyzed much more rapidly and more extensively than unfractionated corn starch. Although the beta dextrins were hydrolyzed by this amylase, they were hydrolyzed much more slowly and less extensively than either of the other two substrates. These results are similar to those already considered for pancreatic amylase.41 64... 

Amylose, another natural polysaccharide, prepared under appropriate conditions, is not only able to produce films, but is also found to be resistant to the action of pancreatic a-amylase while remaining vulnerable to the colonic flora [82]. However, incorporation of ethylcellulose was necessary to prevent premature drug release through simple diffusion [83], In vitro release of 5-aminosalicylic acid from pellets coated with a mixture of amylose-ethylcellulose in a ratio of 1 4 was complete after 4 hr in a colonic fermenter. By contrast, it took more than 24 hr to release only 20% of the drug under conditions that mimic that of the stomach and of the small intestine. 

While pancreatic and malt amylases are similar in their protein nature and alike in yielding maltose as the chief end product of their action upon starch, there are some respects in which they present marked differences. Thus the optimum activities of these two enzymes are shown at quite different hydrogen ion concentrations that of pancreatic amylase in a practically neutral solution, pH = 6.9 that of malt amylase at the distinctly acid reaction of pH = 4.411 In an extended series of experiments with malt amylase it was found that the optimum hydrogen ion concentration was the same whether this were reached by the addition of a strong acid, a weak acid, or an acid salt.12... 

Protein and starch digestion, on the other hand, have potent nonpancreatic compensatory mechanisms. Due to the compensatory action of salivary amylase and brush border oligosaccharidases, a substantial proportion of starch digestion can be achieved without pancreatic amylase. Similarly, protein denaturation and hydrolysis is initiated by gastric proteolytic activity (acid and pepsin) and continued by intestinal brush border peptidases, and is thus partly maintained even in the absence of pancreatic proteolytic activity. 

The primary functions of the small intestine are digestion and absorption of food. The adult small intestine is approximately 6 m in length and is composed of the duodenum, ileum, and jejunum. Digestion occurs primarily in the upper small intestine and requires the action of pancreatic enzymes such as amylase, lipase, and trypsin, which are released from the pancreas into the duodenum, and bile salts from the biliary system. Absorption largely takes place in lower portions of the small intestine. 

It is now generally accepted that the digestion of starch by many mammalian species involves, firstly, the action of pancreatic oc-amylase to give oligosaccharide end-products which are hydrolysed further to D-glucose by the enzymes of the small intestine brush border. The enzymology of these reactions has been reviewed" with respect to both nutritional and clinical implications. 

A large amount of amylase inhibitors, of at least four kinds, were produced by Streptomyces sp. No. 280 when cultivated on 3% oatmeal medium and it was found that the molecular weight of the inhibitors were transformed to small molecules during the cultivation time. The transformation of the amylase inhibitor was found to result from degradation of its carbohydrate moiety by a-amylase in the culture broth. The amylase inhibitor was hydrolysed partially by the action of Taka-amylase A or hog pancreatic a-amylase. With hydrolysa-tion of amylase inhibitor by a-amylase, neutral sugars (mainly maltose) were... 

Several models have been proposed to account for the non-random distribution of oligosaccharides formed when polysaccharides are hydrolysed by a-amylase. The preferred-attack model assumes that the probability of bond-cleavage depends on the position of the bond in the chain the repetitive (or multiple-attack) model assumes that a-amylase can form a cage-like complex with the substrate and attack it several times during a single encounter the multiple-enzyme (or dual-site) model assumes that the substrate is hydrolysed by the combined actions of exo- and en /o-enzymes. The effects of pH, inhibitors, and the chain length of the substrates have been studied in an attempt to decide which of the three models best fits the action of a-amylase. The effects of these variables on either the distribution of products or the action pattern of the enzyme were incorporated into the models, which were then used to interpret experimental data obtained with porcine pancreatic a-amylase. 

The answer is d. (Hardman, p 935.) Pancrelipase is an alcoholic extract of hog pancreas that contains lipase, trypsin, and amylase. It is effective in reducing the steatorrhea of pancreatic insufficiency None of the other drugs mentioned have significant action in the digestion of fats... 

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