Purification and Characterization of a Novel α-Glucuronidase from<i>Aspergillus niger</i>Specific for<i>O</i>-α-<scp>D</scp>-Glucosyluronic Acid α-<scp>D</scp>-Glucosiduronic Acid
作者:Takaaki KIRYU、Hirofumi NAKANO、Taro KISO、Hiromi MURAKAMI
DOI:10.1271/bbb.69.522
日期:2005.1
A new α-glucuronidase that specifically hydrolyzed O-α-D-glucosyluronic acid α-D-glucosiduronic acid (trehalose dicarboxylate, TreDC) was purified from a commercial enzyme preparation from Aspergillus niger, and its properties were examined. The enzyme did not degrade O-α-D-glucosyluronic acid α-D-glucoside, O-α-D-glucosyluronic acid β-D-glucosiduronic acid, O-α-D-glucosyluronic acid-(1→2)-β-D-fructosiduronic acid, p-nitrophenyl-O-α-D-glucosiduronic acid, methyl-O-α-D-glucosiduronic acid, or 6-O-α-(4-O-α-D-glucosyluronic acid)-D-glucosyl-β-cyclodextrine. Furthermore, it showed no activity on α-glucuronyl linkages of 4-O-methyl-D-glucosyluronic acid-α-(1→2)-xylooligosaccharides, derived from xylan, a supposed substrate of α-glucuronidases.The molecular mass of the enzyme was estimated to be 120 kDa by gel filtration and 58 kDa by SDS–PAGE suggesting, the enzyme is composed of two identical subunits. It was most active at pH 3.0–3.5 and at 40 °C. It was stable in pH 2.0–4.5 and below 30 °C. It hydrolyzed O-α-D-glucosyluronic acid α-D-glucosiduronic acid to produce α- and β-anomers of D-glucuronic acid in an equimolar ratio. This result suggests that inversion of the anomeric configuration of the substrate is involved in the hydrolysis mechanism.
一种新的α-葡萄糖醛酸酶从黑曲霉的商业酶制备物中纯化而得,特异性水解O-α-D-葡萄糖基醛酸α-D-葡萄糖醛酸(甘露糖二羧酸,TreDC),并对其性质进行了研究。该酶未能降解O-α-D-葡萄糖基醛酸α-D-葡萄糖苷、O-α-D-葡萄糖基醛酸β-D-葡萄糖醛酸、O-α-D-葡萄糖基醛酸-(1→2)-β-D-果糖醛酸、对硝基苯基-O-α-D-葡萄糖醛酸、甲基-O-α-D-葡萄糖醛酸或6-O-α-(4-O-α-D-葡萄糖基醛酸)-D-葡萄糖基-β-环糊精。此外,它对来自木聚糖的4-O-甲基-D-葡萄糖基醛酸-α-(1→2)-木寡糖的α-葡萄糖醛酸键没有活性,这被认为是α-葡萄糖醛酸酶的一个假定底物。通过凝胶过滤法估计,该酶的相对分子质量为120 kDa,而通过SDS-PAGE估计为58 kDa,表明该酶由两个相同的亚基组成。其在pH 3.0–3.5和40 °C时活性最强,并在pH 2.0–4.5及低于30 °C条件下稳定。它将O-α-D-葡萄糖基醛酸α-D-葡萄糖醛酸水解生成等摩尔比例的α-和β-异构体D-葡萄糖醛酸。该结果表明,底物的异构配置反转参与了水解机制。