Jeanningros R, Creuzet-Sigal N, Frixon C, Cattaneo J
Biochim Biophys Acta. 1976 Jun 7;438(1):186-99. doi: 10.1016/0005-2744(76)90235-7.
The debranching enzyme (EC 3.2.1.-) from Escherichia coli K12 was purified 312-fold with a 21% yield, DEAE-cellulose and DEAE-Sephadex chromatography were used for purification. The preparation was homogeneous and showed only a single band of protein and activity upon polyacrylamide gel electrophoresis. The enzyme hydrolyzed 1,6-alpha-glucosidic linkages in phosphorylase and beta-amylase limit dextrins prepared from glycogen and amylopectin. Small branched oligosaccharides were also hydrolyzed. Amylopectin was also completely hydrolyzed but the enzyme showed only a very low activity with glycogen as the substrate. The enzyme cannot be classified as a pullulanase because it has practically no activity with pullulan. But it also differs from the bacterial isoamylases described in other studies because of its inability to hydrolyze glycogen. The optimal pH is about 5.6. The optimal growth conditions for the synthesis of the enzyme by E. coli were also examined in the present studies.
从大肠杆菌K12中纯化出的脱支酶（EC 3.2.1.-），纯化倍数为312倍，产率为21%，采用DEAE - 纤维素和DEAE - 葡聚糖凝胶色谱法进行纯化。该制剂在聚丙烯酰胺凝胶电泳中表现为均一，仅出现一条蛋白质和活性条带。该酶可水解磷酸化酶以及由糖原和支链淀粉制备的β - 淀粉酶极限糊精中的1,6 - α - 糖苷键。小的分支寡糖也能被水解。支链淀粉也能被完全水解，但该酶以糖原作为底物时活性极低。该酶不能归类为普鲁兰酶，因为它对普鲁兰几乎没有活性。但它也与其他研究中描述的细菌异淀粉酶不同，因为它不能水解糖原。最适pH约为5.6。本研究还考察了大肠杆菌合成该酶的最佳生长条件。
