Applied Microbiology and Biotechnology, Vol.103, No.2, 807-817, 2019
Study on expression and action mode of recombinant alginate lyases based on conserved domains reconstruction
Understanding the effect of conserved domains reconstruction of alginate lyases on action mode is essential for their application and in-depth study. We report the expression and action mode of recombinant alginate lyase (AlyM) and its conserved domain reconstruction forms (AlyMCBM, cAlyM, and AlyM58C). The enzymatic activities of AlyM, AlyMCBM, cAlyM, and AlyM58C were 61.77, 150.57, 388.97, and 308.21U/mg, respectively. The transcription level of cAlyM was 49.89-fold of AlyM. cAlyM and AlyM58C showed higher thermal stability than AlyM, indicating that the removal of F5_F8_type_C domain was beneficial for the increase of thermal stability. The enzymes were bifunctional alginate lyases and preferred polyG to polyM. The enzymes degraded alginate to produce unsaturated disaccharide, trisaccharide, and tetrasaccharide as the main end-products. Pentamannuronic acid and pentaguluronic acid were the smallest substrates that could be degraded by AlyM, with unsaturated trisaccharide/tetrasaccharide (40.61%/44.42%) and disaccharide/trisaccharide (10.57%/83.85%) as the main products, respectively. The action modes of enzymes remain unaffected after conserved domain reconstruction, but the affinity of AlyM58C toward polyM increased. This study provides a new strategy for rational modification of alginate lyase based on conserved domain reconstruction.