Pancreatitis Amylase

The hydrolysis of starch by salivary and pancreatic amylases catalyze random hydrolysis of a(l—>4) glycoside bonds, yielding dextrins, then a mixmre of glucose, maltose, and isomaltose (from the branch points in amylopectin). 

Some of the pancreatic enzymes in the lumen include pancreatic amylase, pancreatic lipase, elastase, trypsin, a-chymotrypsin, and carboxypeptidase A. For example, the aspirin derivatives aspirin phenylalanine ethyl ester, aspirin phenyllactic ethyl ester, and aspirin phenylalanine amide have been studied as substrates for carboxypeptidase A [67,68], with the phenylalanine ethyl ester derivative proving to be the best substrate. This study indicated that the carboxypeptidase A may serve as a reconversion site for many drug derivatives. 

While alpha amylases from many sources are known, the present discussion will deal mainly with the alpha amylase of malted barley, pancreatic amylase and the amylase of Aspergillus oryzae. These... 

Pancreatic amylase is very labile and sensitive to its chemical environment. Its lability is accelerated by purification and by such factors as dilution of its aqueous solutions, dialysis of its aqueous solutions against water, unfavorable hydrogen ion activities and unfavorable temperatures.29-31, 36,33 The loss of amylase activity in solutions of pancreatic amylase increases with increasing temperature and is very rapid between 50° and 60°. The inactivation of pancreatic amylase in aqueous solution may be retarded by the addition of certain anions, of which the chloride ion is outstanding 37-39 by the addition of certain cations, of which... 

Reacting mixtures of pancreatic amylase and starch exhibit alpha mutarotation.48 49... 

Conditions Which Favor Activity.—Not only the stability but the activity of pancreatic amylase is dependent upon its chemical environment. The general statement may be made that pancreatic amylase is... 

Early evidence showed that electrolyte was needed for the activation of pancreatic amylase.60 Later evidence showed that certain anions... 

Comparison of the Influence of Certain Ions upon the Activity of Pancreatic Amylase (Data of Sherman, Caldwell and Adams89)... 

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. 

Pancreatic amylase is so far the only amylase which has been found to be completely inactive in the absence of certain anions.39,60 Other amylases of animal origin, such as salivary and blood amylases, show increased activity in the presence of electrolyte61,62 and, when highly purified, may also be found to require the presence of certain anions for their activation. Kneen and coworkers68,64 have reported the purifica-... 

Alpha amylases cause a rapid fragmentation of starch with an accompanying marked decrease in viscosity of the starch solutions. Therefore, viscosity determinations may be used to follow the early stages in the hydrolysis of starch by these amylases. Afthough this type of measurement is of considerable importance for certain industrial applications, it has not been used to any great extent in investigations with pancreatic amylase. 

The ratio of dextrinogenic to saccharogenic activities for pancreatic amylase, measured with Lintner s soluble potato starch under comparable conditions at 40°, is approximately 2 to 45,57 The achroic point is reached in the hydrolysis of potato starch by highly purified pancreatic amylase when approximately 20% of the glucose linkages of the starch have been broken.41... 

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... 

Influence of Dialysis During Hydrolysis upon the Extent of the Hydrolysis of Lintner s Soluble Potato Starch by Pancreatic Amylase (Data of Alfin and Caldwell 1)... 

The addition of more pancreatic amylase to reaction mixtures that had been dialyzed during the hydrolysis and that had reached stages of... 

On the other hand, marked inactivation of the amylase (86 to 87 %) occurred when solutions of the same purified pancreatic amylase preparations were dialyzed under the same conditions but in the absence of substrate.41 These results give experimental evidence for the suggestion often advanced that the amylase unites with its substrate, in this case with the larger less readily dialyzable products of the hydrolysis of starch, and thus is protected from appreciable inactivation due to dialysis. 

The results of this work as a whole indicate that the slowing down of the hydrolysis of starch by pancreatic amylase is due largely to the replacement of the original substrate by products for which the amylase has relatively low affinities. 

Products.—Considerable information concerning the mechanism of the enzymic hydrolysis of starch has been obtained from investigations of the action of purified maltase-free pancreatic amylase on a number of different substrates. The substrates studied were ordinary unfractionated but exhaustively defatted10 potato and com starches a branched chain substrate, waxy maize starch and amylose, the linear component of corn starch.41 69 eo f4 These investigations included comparisons not only of the rates of the hydrolysis of the different substrates but also of the products formed from them. 

With the same concentration of pancreatic amylase reacting under comparable conditions, no marked differences were observed in the rate of the hydrolysis of any of the unfractionated ordinary starches studied.41,69 6064 On the other hand significant differences were observed in the rate of the hydrolysis of straight and of branched chain substrates. The data60 in Table IV show that waxy maize starch is hydrolyzed more slowly than unfractionated corn starch and much more slowly than the... 

A Comparison of the Action of Purified Maltase-free Pancreatic Amylase on Waxy Maize Starch and on Other Substrates (Data of Mindell, Agnew and CcddwellM)... 

The data given in Table V show not only that pancreatic amylase hydrolyzes unfractionated starch and a linear substrate at different rates but also that, for equivalent time intervals with the same concentration of pancreatic amylase, the relative concentrations of the products formed from these two substrates differ. In addition, Table VIM,M summarizes comparative data for the products of the hydrolyses of potato starch, of com amylose, and of waxy maize starch when equivalent numbers of glucosidic linkages of these substrates had been broken. 

Maltose is liberated by pancreatic amylase in measurable concentra-... 

Products Formed from Potato Starch, from Waxy Maize Starch and from Corn Amylose by Purified Maltose-free Pancreatic Amylase... 

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