Characterization of a novel β-agarase from an agar-degrading bacterium Catenovulum sp. X3
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An agar-degrading bacterium, Catenovulum sp. X3, was isolated from the seawater of Shantou, China. A novel β-agarase gene agaXa was cloned from the strain Catenovulum sp. X3. The gene agaXa consists of 1,590 bp and encodes a protein of 529 amino acids, with only 40 % amino acid sequence identity with known agarases. AgaXa should belong to the glycoside hydrolase family GH118 based on the amino acid sequence similarity. The molecular mass of the recombinant AgaXa (rAgaXa) was estimated to be 52 kDa by sodium dodecyl sulfate–polyacrylamide gel electrophoresis. It had a maximal agarase activity at 52 °C and pH 7.4 and was stable over pH 5.0 ~ 9.0 and at temperatures below 42 °C. The K m and V max for agarose were 10.5 mg/ml and 588.2 U/mg, respectively. The purified rAgaXa showed endolytic activity on agarose degradation, yielding neoagarohexaose, neoagarooctaose, neoagarodecaose, and neoagarododecaose as the end products. The results showed that AgaXa has potential applications in agar degradation for the production of oligosaccharides with various bioactivities.
KeywordsAgarase Catenovulum sp. X3 Gene Expression
This work was supported by the National Natural Science Foundation of China (nos. 41076106 and 31200077), Guangdong Natural Science Foundation (no. S2011030005257), and the Key Science and Technology Innovation Project for University by the Department of Education of Guangdong Province (no. CXZD1124) and the Science & Technology Project of Guangdong Province (no. 2012A031100009).
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