Dong Qi, Ruan Lingwei, Shi Hong
State Key Laboratory Breeding Base of Marine Genetic Resources, Key Laboratory of Marine Genetic Resources of State Oceanic Administration, Third Institute of Oceanography, State Oceanic Administration, Key Laboratory of Marine Genetic Resources of Fujian Province, South China Sea Bio-Resource Exploitation and Utilization Collaborative Innovation Center, Xiamen, 361005, PR China.
State Key Laboratory Breeding Base of Marine Genetic Resources, Key Laboratory of Marine Genetic Resources of State Oceanic Administration, Third Institute of Oceanography, State Oceanic Administration, Key Laboratory of Marine Genetic Resources of Fujian Province, South China Sea Bio-Resource Exploitation and Utilization Collaborative Innovation Center, Xiamen, 361005, PR China.
Carbohydr Res. 2016 Sep 2;432:1-8. doi: 10.1016/j.carres.2016.05.002. Epub 2016 May 14.
A novel endo-type β-agarase, AgaB, was cloned from an agar-degrading bacterium, Flammeovirga sp. SJP92. The gene agaB consists of 2, 550 bp and encodes a protein of 849 amino acids including a 19 amino acids signal peptide. Based on the amino acid sequence similarity, AgaB belongs to the glycoside hydrolase family GH16. The recombinant AgaB was expressed in Escherichia coli and exhibited maximal activity at around 45 °C and pH 8.0, with a specific activity of 254.2 U/mg, a Km of 3.99 mg/ml and a Vmax of 700 U/mg for agarose. The agarase was stable at neutral to mildly alkaline condition, and remained 85%-90% of activity after treatment for 1 h, a characteristic much more different from other agarases reported. The recombinant enzyme was sensitive to some metal ions (Cu(2+), Co(2+) and Zn(2+)), but resistant to some denaturants (urea and SDS). It can hydrolyze the β-1, 4-glycosidic linkages of agarose, yielding neoagarotetraose and neoagarohexaose as the main products. These properties could make AgaB has a potential application in the food, cosmetic and medical industries.
从琼脂降解菌火焰弧菌属（Flammeovirga sp.）SJP92中克隆出一种新型内切型β-琼脂酶AgaB。agaB基因由2550个碱基对组成，编码一个含849个氨基酸的蛋白质，其中包括一个19个氨基酸的信号肽。基于氨基酸序列相似性，AgaB属于糖苷水解酶家族GH16。重组AgaB在大肠杆菌中表达，在约45℃和pH 8.0时表现出最大活性，对琼脂糖的比活性为254.2 U/mg，Km为3.99 mg/ml，Vmax为700 U/mg。该琼脂酶在中性至弱碱性条件下稳定，处理1小时后仍保留85%-90%的活性，这一特性与其他已报道的琼脂酶有很大不同。重组酶对一些金属离子（Cu(2+)、Co(2+)和Zn(2+)）敏感，但对一些变性剂（尿素和SDS）有抗性。它能水解琼脂糖的β-1,4-糖苷键，产生新琼脂四糖和新琼脂六糖作为主要产物。这些特性可能使AgaB在食品、化妆品和医药行业具有潜在应用价值。
