Biochemical Characterization and Elucidation of the Hybrid Action Mode of a New Psychrophilic and Cold-Tolerant Alginate Lyase for Efficient Preparation of Alginate Oligosaccharides.

Alginate lyases with unique biochemical properties have irreplaceable value in food and biotechnology industries. Herein, the first new hybrid action mode -derived alginate lyase gene (TAPL7A) with both psychrophilic and cold-tolerance was cloned and expressed heterologously in . With the highest sequence identity (43%) to the exolytic alginate lyase AlyA5 obtained from , TAPL7A was identified as a new polysaccharide lyases family 7 (PL7) alginate lyase. TAPL7A has broad substrate tolerance with specific activities of 4186.1 U/mg, 2494.8 U/mg, 2314.9 U/mg for polyM, polyG, and sodium alginate, respectively. Biochemical characterization of TAPL7A showed optimal activity at 15 °C, pH 8.0. Interestingly, TAPL7A exhibits both extreme psychrophilic and cold tolerance, which other cold-adapted alginate lyase do not possess. In a wide range of 5-30 °C, the activity can reach 80-100%, and the residual activity of more than 70% can still be maintained after 1 h of incubation. Product analysis showed that TAPL7A adopts a hybrid endo/exo-mode on all three substrates. FPLC and ESI-MS confirmed that the final products of TAPL7A are oligosaccharides with degrees of polymerization (Dps) of 1-2. This study provides excellent alginate lyase candidates for low-temperature environmental applications in food, agriculture, medicine and other industries.