Amylases from malt

Very highly purified preparations of alpha amylase of malted barley give a value of approximately 4 to 1 for the ratio of their dextrinogenic to their saccharogenic activities when the measurements are made at 40° with Lintner s soluble potato starch.81 Under the same conditions approximately the same value is obtained with products precipitated by alcohol from malted barley extracts which had been treated to inactivate beta amylase.23 81 However, a constant value for these ratios is not proof that beta amylase is entirely absent. There is at present no satisfactory way of making certain that malted barley alpha amylase is not contaminated with traces of beta amylase. The crystallization of alpha amylase from malted barley has been reported since this manuscript was written.79... 

A Comparison of the Action of Purified Maltase-free Alpha Amylase from Malted Barley upon Corn Amylose, Corn Starch and upon Beta Dextrins Formed from Corn Starch by the Action of Beta Amylase (Data of Myrbdck and Thorsellu)... 

Nirmala, M. and Muralikrishan, G. (2003a). Properties of three purified a-amylases from malted finger millet (ragi, Eleusine coracana, Indaf-15). Carbohydr. Polym. 54, 43-50. 

Source. Enzymes for food applications come from all three kingdoms plant, animal, and microbial. Traditionally used plant and animal enzymes are the plant proteases such as papain, ficin and bromelain, plant amylases from malt, and animal rennin which is used in cheese manufacture. Microbial cells are the usual and most promising future source of industrial enzymes. Estimates of the number of microorganisms in the world tested as potential sources of enzymes fall around 2% with only about 25 organisms, including a dozen or so fungi, currently used for industrial enzymes. 

From the variation of with temperature (when Michaelis conditions hold), the heat and entropy of formation of the enzyme — substrate complex can be found. Such calculations have been made for the alpha-amylase from pig pancreas, and the alpha- and beta-amylases from malted sorghum. ... 

The inhibition of aZp/ta-amylases from malt barley and hog pancreas by maltose has been shown to be noncompetitive, as has the inhibition of the malt-barley enzyme by a limit dextrin obtained by... 

Such processes have existed for many thousands of years in the manufacture of cheese from milk and in the brewing of beer from barley. In the former process the enzyme chymosin catalyses the hydrolysis of one peptide bond in casein, causing the milk to clot, and in the latter the amylases from malted barley (the diastases of Peyen and Persoz) catalyse the hydrolysis of starch. While these remain important processes the application of enzymes such as these to industrial chemistry is quite recent, dating back only to about 1960. 

In 1833 an amylase from germinating barley was recovered and called diastase (1). Like malt itself, this product converted gelatinized starch into sugars, primarily maltose. Shordy thereafter, BerzeHus proclaimed the existence of non-living catalysts, and Schwaim (2) reported on his observation and purification of pepsin. 

Fischer, brilliant results were achieved, and in succession the a-amylases of pig pancreas, of Bacillus subtilis, of human saliva, of human pancreas, and of Aspergillus oryzae, and the /3-amylase of malt, were successfully crystallized. Important biological deductions were gained from this study whereas the amylases of human pancreas and saliva cannot be distinguished from one another, amylases from pig pancreas and from human pancreas are different. These differences are manifested in molecular weight, crystalline forms, electrophoretic mobility, and influence of the pH on the activity however, all the amylases have the same specific biochemical action. The identity of the enzymes seems to be dependent on the species and not on the organ. Interest in biologically active proteins led Meyer to a study of the protein hormones, a field in which he was very active at the time of his death. 

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... 

Examination of the ratios of the dextrinogenic to the saccharogenic activities of malted barley extracts before and after treatment shows that the results of the Ohlsson procedures23 are not always predictable.8 The concentration of the amylases in the extracts, and the kinds and concentrations of substances which accompany them, influence the results. The presence or the absence of calcium ions is an important factor. Calcium ions increase the inactivation of beta amylase of malted barley and protect the alpha amylase from inactivation at unfavorable temperatures and also at unfavorable hydrogen ion activities.28 With purification, both amylases become increasingly thermolabile and increasingly sensitive to unfavorable hydrogen ion activities.78... 

The alpha amylase of malted barley causes a rapid decrease in the viscosity of its substrates and the rapid disappearance from its reaction mixtures of products which give color with iodine. Myrback80 reports a drop of 50% in the relative viscosity of potato starch when only approximately 0.1% of the glucose linkages of the substrate had been ruptured under the influence of this amylase. The achroic point for reactions of malted barley alpha amylase usually is stated to occur at approximately 30% theoretical maltose.13 In contrast, the achroic point is reached with pancreatic amylase at 40% and with the amylase of Aspergillus oryzae at 25%.41,73... 

Arrow root starch, approximately 2% pH 5.3 amylase prepared from malted barley extract according to Ohlsson23 and purified by precipitation with alcohol. 

Products Formed by Malted Barley Alpha Amylase from Beta Dextrine Formed from Arrowroot Starch by Beta Amylase (Data of Myrbiicku)... 

A different method was developed for the purification of pancreatic amylase.4 This enzyme differs somewhat in its solubilities and considerably in the conditions governing its activity, from the corresponding enzyme of malt but the purified amylase preparations from the pancreas and from malt are much alike in respect to the chemical properties above mentioned. Pancreatic amylase is much less stable than malt amylase and much more quickly suffers a loss or diminution of enzymic activity in solution, which as in the case of malt amylase appears to be due, at least chiefly, to hydrolysis of the enzyme molecule. 

Pancreatic amylase is more sensitive than malt amylase both in the sense that it loses its activity much more rapidly when held in aqueous dispersion, and that it is active only within a narrower range of hydrogen ion concentration. When the two amylases are tested in purified condition upon a dispersion of soluble starch at a temperature of 40°, and each in the presence of its optimum concentration of hydrogen ion and of chloride and phosphate, the enzymic activity of the amylase of the pancreas is fully twice that of the amylase of malt, fairly constant quantitative values being shown in numerous preparations of each enzyme made at different times and in several cases from different specimens of the original material. 

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