Igarashi T, Yamamoto A
Showa Shigakkai Zasshi. 1988 Dec;8(4):405-12.
Multiple forms of dextranase were detected in both intra- and extracellular fractions of Bacteroides oralis Ig4a. The molecular weights of these enzymes varied from 52,000 to 260,000 by sodium dodecyl sulfate-polyacrylamide-blue dextran gel electrophoresis. The intracellular dextranases were fractionated by chromatography and gel filtration steps, and the dextranases IV and V were obtained. The former was only partially pure. The molecular weights of the dextranases IV and V were estimated to be 120,000 and 105,000, respectively, by SDS-PAGE. The dextranase V was further characterized and it was revealed that the pH- and temperature optima were 5.0, and 55 degrees C, respectively. The Km value was 6.7 x 10(-2) mM for dextran T-70. The enzyme did not exhibit any metal ion requirements, but was inhibited by CoCl2 and HgCl2; lysine and alanine contents were especially high; it hydrolyzed the alpha-1,6-glucan by an exo-type mechanism, and was inactive toward glucans containing alpha-1,3-, alpha-1,4-, and beta-1,4-linkages.
在口腔拟杆菌Ig4a的细胞内和细胞外部分均检测到多种形式的右旋糖酐酶。通过十二烷基硫酸钠-聚丙烯酰胺-蓝色葡聚糖凝胶电泳，这些酶的分子量在52,000至260,000之间。细胞内的右旋糖酐酶通过色谱和凝胶过滤步骤进行分离，得到了右旋糖酐酶IV和V。前者只是部分纯化。通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）估计，右旋糖酐酶IV和V的分子量分别为120,000和105,000。对右旋糖酐酶V进行了进一步表征，结果显示其最适pH值和温度分别为5.0和55℃。对于右旋糖酐T-70，其米氏常数（Km）值为6.7×10⁻² mM。该酶不需要任何金属离子，但受到氯化钴和氯化汞的抑制；赖氨酸和丙氨酸含量特别高；它通过外切型机制水解α-1,6-葡聚糖，对含有α-1,3-、α-1,4-和β-1,4-键的葡聚糖无活性。
