Laboratory of Marine Biotechnology and Microbiology, Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido, 041-8611, Japan.
Comp Biochem Physiol B Biochem Mol Biol. 2010 Sep;157(1):137-43. doi: 10.1016/j.cbpb.2010.05.012. Epub 2010 Jun 4.
A mannan-degrading enzyme was isolated from the digestive fluid of the common sea hare Aplysia kurodai by ammonium sulfate fractionation followed by conventional column chromatography. The purified enzyme, named AkMan in the present paper, showed a single band with an approximate molecular mass of 40,000 Da on SDS-PAGE and preferably degraded a linear beta-1,4-mannan from green algae Codium fragile producing tri- and disaccharides. The optimal temperature of AkMan was 55 degrees C at pH 7.0 and temperature that caused 50% inactivation of AkMan during a 20-min incubation was 52 degrees C. AkMan retained high activity at pH 4.0-7.5 and was not inactivated in such acidic pH range by the incubation at 40 degrees C for 20 min. AkMan could degrade glucomannan from konjak root and galactomannan (tara gum and guar gum) as well as the linear beta-1,4-mannan, while not carboxymethyl cellulose, agarose, dextran and xylan. These results indicate that AkMan is a typical endo-beta-1,4-mannanase (EC 3.2.1.78) splitting internal beta-1,4-mannosyl linkages of mannan. The N-terminal and internal amino-acid sequences of AkMan shared approximately 55% amino-acid identity to the corresponding sequences of an abalone beta-1,4-mannanase, HdMan, which belongs to glycosyl hydrolase family 5 (GHF5). Thus, AkMan was also regarded as a member of GHF5 beta-1,4-mannanases.
一种甘露聚糖降解酶从普通海兔 Aplysia kurodai 的消化液中通过硫酸铵分级和常规柱层析分离得到。本文将该纯化酶命名为 AkMan，它在 SDS-PAGE 上显示出一个约 40,000 Da 的单带，并且优先降解来自绿藻 Codium fragile 的线性β-1,4-甘露聚糖，产生三糖和二糖。AkMan 的最适温度为 55°C，在 pH7.0 下，50%的 AkMan 在 20 分钟孵育中失活的温度为 52°C。AkMan 在 pH4.0-7.5 下保持高活性，并且在 40°C 孵育 20 分钟的酸性 pH 范围内不会失活。AkMan 可以降解魔芋根中的葡甘露聚糖和半乳甘露聚糖（塔拉胶和瓜尔胶）以及线性β-1,4-甘露聚糖，而不降解羧甲基纤维素、琼脂糖、葡聚糖和木聚糖。这些结果表明 AkMan 是一种典型的内切β-1,4-甘露聚糖酶（EC 3.2.1.78），可裂解甘露聚糖的内部β-1,4-甘露糖苷键。AkMan 的 N 末端和内部氨基酸序列与鲍鱼β-1,4-甘露聚糖酶 HdMan 的相应序列约有 55%的氨基酸同一性，HdMan 属于糖苷水解酶家族 5（GHF5）。因此，AkMan 也被认为是 GHF5β-1,4-甘露聚糖酶的成员。
