Untitled research work

Many pullulan-hydrolyzing enzymes have been purified from several microorganisms and higher plants since 1961 when Bender and Wallenf els found pullulanase (EC 3.2.1.41 pullulan 6-glucanohydrolase) in culture filtrate of Aerobacter aerogenes. They are classified into four groups according to their substrate specificities, that is, the types of glucoamylase (EC 3.2 .1.3 1, 4-α-glucan glucanohydrolase), pullulanase, isopullulanase (EC 3.2. 1.54 pullulan 4-glucanohydrolase) and the Thermoactinontyces vulgaris α-amylase that produces panose from pullulan. Three kinds of enzymes described above, except glucoamylase, are considered to be the specific enzymes acting on α-1, 6-glucosidic linkages or α-1, 4-glucosidic linkages adjacent to α-1, 6-glucosidic linkages of starch, glycogen and oligosaccharides. In this paper, the progress of researches concerning pullulanase, isopullulanase and the Thernmactinomyces α-amylase is summarily described and, in particular, rough estimation of subsites of two pullulanases and isopullulanase was performed on the basis of data that have hitherto been reported. It is suggested that Streptococcus mitis pullulanase, A. aerogenes pullulanase and Aspergillus niger isopullulanase have at least seven, six and four subsites, respectively.