Biochemical Characterization of a New β-Agarase from Cellulophaga algicola

• Published in: International Journal of Molecular Sciences
• Main Authors: Zhenggang Han, Yuxi Zhang, Jiangke Yang
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2019
• Subjects: agar; agarose; β-agarase; glycoside hydrolase; neoagarooligosaccharide; Biology (General); QH301-705.5; Chemistry; QD1-999; Antarctic; Antarc*
• Online Access: https://doi.org/10.3390/ijms20092143; https://doaj.org/article/77cefb7d7a4f4c6f813e257e1f7d1c1f

Cellulophaga algicola DSM 14237, isolated from the Eastern Antarctic coastal zone, was found to be able to hydrolyze several types of polysaccharide materials. In this study, a predicted β-agarase ( Ca Aga1) from C. algicola was heterologously expressed in Escherichia coli . The purified recombinant Ca Aga1 showed specific activities of 29.39, 20.20, 14.12, and 8.99 U/mg toward agarose, pure agar, and crude agars from Gracilaria lemaneiformis and Porphyra haitanensis , respectively. Ca Aga1 exhibited an optimal temperature and pH of 40 °C and 7, respectively. Ca Aga1 was stable over a wide pH range from 4 to 11. The recombinant enzyme showed an unusual thermostability, that is, it was stable at temperature below or equal to 40 °C and around 70 °C, but was thermolabile at about 50 °C. With the agarose as the substrate, the K m and V max values for Ca Aga1 were 1.19 mg/mL and 36.21 U/mg, respectively. The reducing reagent (dithiothreitol) enhanced the activity of Ca Aga1 by more than one fold. In addition, Ca Aga1 was salt-tolerant given that it retained approximately 70% of the maximum activity in the presence of 2 M NaCl. The thin layer chromatography results indicated that Ca Aga1 is an endo-type β-agarase and efficiently hydrolyzed agarose into neoagarotetraose (NA4) and neoagarohexaose (NA6). A structural model of Ca Aga1 in complex with neoagarooctaose (NA8) was built by homology modeling and explained the hydrolysis pattern of Ca Aga1.