抄録
1. "Amylase" should be defined as 'starch-hydrolyzing enzyme.' They necessarily hydrolyzeα-1, 4 and/or α-1, 6 glucoside linkage(s). Oligosaccharides can be substrates of amylases, while the rate of hydrolysis may depend on the chain length and the mode of branching of oligosaccharides. Debranching enzymes, isoamylase and pullulanase are, therefore, to be classified to amylases. 2. “α-Glucosidases” may well be differentiated from amylases, although some of the enzymescan hydrolyze not only short chain oligosaccharides but also starch as well, like glucoamylase. Conventionally, discrimination between α-glucosidase and glucoamylase seems to be made on the basis of the degree of polymerization (DP) of ‘good’ substrates. However, this is marginal and confusing in some cases. The anomer form of the released product must be the most definite and reliable criterion for the discrimination between α-glucosidase and glucoamylase. 3. Condensation is merely the reverse process of hydrolysis. It should clearly be differentiated from glucosyl transfer, although products of DP higher than starting substrates can beformed via either mechanism. The notion that hydrolases may be included in transferases in the sense that hydrolysis is a transfer to water is not incorrect, but is practically inconvenient. Amylases may have more or less transferring activity. Cyclomaltodextrin glucanotransferase [EC2.4.1.19, one of the other names, Bacillus macerans amylase] is classified into transferase, butit may better be classified into amylase since it does actually hydrolyze starch. 4. The present numbering of glycohydrolases are not unified with respect to the order of arrangement: 3.2.1. grouping is natural but the fourth numbers are confused; for example, amylases are distributed in several parts. Rearrangement and renumbering should urgently beconsidered. 5. Useful and important criteria for classification of amylases will be, (a) hydrolyzing ability of α-1, 4 and/or α-1, 6 glucosidic linkage(s), (b) exo- or endo-type in splitting mode, and (c) the anomeric form of the product.
