Aspergillus oryzae a-amylase

Of the animal amylases only the three discussed above have been obtained in crystalline form. Amylase activity, however, is widespread among the animal kingdom. It is also present in human blood plasma and in urine. Molds and bacteria contain a-amylases. Aspergillus oryzae is the source of commericial takadiastase. The reviews of Myrback and Neumuller and of Bernfeld should be consulted for additional information on amylases. 

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. 

The amylase of Aspergillus oryzae causes a very rapid decrease in the viscosity of its substrates and a very rapid disappearance from its reaction mixtures of products which give color with iodine. When examined under favorable conditions71 at 40° with Lintner s soluble potato starch, the achroic point was reached with highly purified maltase-free amylase when approximately 12% of the glucose linkages of the substrate had been ruptured. 

The data show that the extent of the hydrolysis of starch by the amylase of Aspergillus oryzae depends within wide limits upon the concentration of amylase used. Like those for pancreatic amylase already discussed (Figure 2), these hydrolysis curves show a change from a rapid to a slow phase of the reaction and tend to flatten at higher values as the concentration of amylase is increased. Again, with different concentrations of the amylase of Aspergillus oryzae there is no evidence of a common limit such as is observed with different concentrations of beta amylase (Figure 1). 

A Comparison of the Hydrolysis of Soluble Potato Starch by Purified Maltase-free Pancreatic Amylase or Amylase of Aspergillus oryzae (Extent of Hydrolysis as Percent Theoretical Maltose)... 

Taken as a whole, the results indicate that the amylase of Aspergillus oryzae causes the rapid random hydrolysis both of the straight and of the branched chain components of starch and that it hydrolyzes very slowly products with average molecular weights of penta- and tetra-saccharides. 

Studies of the rate of the hydrolysis of dextrins isolated from a reaction mixture after the extensive hydrolysis of starch by maltase-free malted barley alpha amylase, led Myrback11 to conclude that the flattening of the reaction curves with this amylase is not due to equilibrium between the amylase and the products of the hydrolysis. As indicated above, similar conclusions have been reached for pancreatic amylase and for the amylase of Aspergillus oryzae.41,7a... 

The most important features are, first, that some of the a-amylases— i.e., those in digests Numbers 4, 5, 6, and 7 have catalyzed glycosylations from a-maltosyl fluoride at one-tenth to one-one hundredth the enzyme concentrations required for action on a-D-glucosyl fluoride. The Aspergillus oryzae a-amylase, which had the weakest synthetic action on a-D-glucosyl fluoride of the enzymes tested at 100 ftg/ml, has produced under conditions of this experiment an extended series of maltosaccharides at 1 fig/ml. 

Tada, S., Iimura, Y., Gomi, K., Takahashi, K., Hara, S., and Yoshizawa, K. (1989). Cloning and nucleotide sequence of the genomic Taka-amylase A gene of Aspergillus oryzae. Agric. Biol. Chem., 53, 593-399. 

Figure 7.12 Identification of the amino acid residues involved in the seven subsite binding of the substrate in the active-site of Aspergillus oryzae a-amylase. The bold faced amino acid residues are those conserved in the active-site of porcine pancreatic a-amylase. (From Matsuura et al. 123 reprinted by permission)...

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