Abstract
1. The action of a-amylase from saliva, and of β-amylase from ungerminated barley on amylose and amylopectin was tested by the potentiometric titration method with iodine. It was proved that the amount of amylose and amylopectin in the reaction mixture could be determined by this method. The action of so-called “amylosynthease” from yeast on waxy rice starch was also tested by this method.
2. As the result of the action of β-amylase on amylose, the amount of the original amylose decreased, but the remaining molecules of amy-lose were the same as those of the original amylose. The sum of the remaining amylose and the maltose produced was the same as the amount of the original amylose. The action was proved to be of the 1st order from the observation of both the amounts of the remaining amylose and the produced maltose.
3. By the action of α-amylase on amylose two sorts of dextrin amylose of a definite but smaller molecular weight were obtained at the early stage of the reaction. Later, from these molecules of dextrin amylose of still smaller molecules were produced. The course of these reactions could be determined from the reducing power of the reaction, mixture and from the amount of the original amylose remaining and the dextrin amylose produced.
4. As the result of the action of β-amylase on amylopectin, amy-lopectin was found to be degradated to a certain extent, at times as much as 50%, leaving the molecules of “limit-dextrin” which still had some but a less ability to adsorb iodine.
5. As the result of the action of α-amylase on amylopectin, still smaller molecules were produced which could not adsorb iodine. The course of this reaction was determined from the amounts of amylopectin present and the increase in the reducing power of the reaction mixture. It was proved that the reaction was of the 1st order at the early stage of the reaction.
6. By the action of so-called “amylosynthease” on waxy rice starch with the branched chain structure, the compounds of linear structure like amylose were produced and their amounts increased with the reaction time. The products consisted of the molecules of different molecular weight and even the largest molecules of the products were smaller than those of potato amylose.
This work was supported by a Grant in Aid for Fundamental Scientific Re-search from the Department of Education.
The author is grateful to Prof. Keizo Kodama for his valuable discussions and Prof. Norio Shimazono for his revision of this paper. The author also wishes to thank Mr. M. Seizi for carrying out the determination of the reducing sugar.
