Biochemical Characterization of a New β-Agarase from .

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 (Aga1) from . was heterologously expressed in . The purified recombinant Aga1 showed specific activities of 29.39, 20.20, 14.12, and 8.99 U/mg toward agarose, pure agar, and crude agars from and , respectively. Aga1 exhibited an optimal temperature and pH of 40 C and 7, respectively. 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 40C and around 70 C, but was thermolabile at about 50 C. With the agarose as the substrate, the and values for Aga1 were 1.19 mg/mL and 36.21 U/mg, respectively. The reducing reagent (dithiothreitol) enhanced the activity of Aga1 by more than one fold. In addition, 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 Aga1 is an endo-type β-agarase and efficiently hydrolyzed agarose into neoagarotetraose (NA4) and neoagarohexaose (NA6). A structural model of Aga1 in complex with neoagarooctaose (NA8) was built by homology modeling and explained the hydrolysis pattern of Aga1.