Two Alginate Lyases from Polysaccharide Lyase Family 44 Exhibited Diversity in Substrate Specificity

Alginate lyases are important tools for alginate biodegradation and oligosaccharide preparation. This study characterized the two alginate lyases, Aly44An and Aly44Pa, from the newly constructed polysaccharide lyase family 44 (PL44). Aly44An exhibited the highest enzyme activity and conversion efficiency for polyM and also showed activity for alginate and polyG. Aly44Pa demonstrated enzyme activity only toward alginate and polyM. Meanwhile, the end products of Aly44An contained ΔG, ΔM, ΔGG, ΔGM, ΔMG, ΔGGG, and ΔMM, while Aly44Pa contained ΔM, ΔMG, and ΔMM. The results of the activity assay, molecular dynamics simulations, and product analysis indicated that Aly44An was an M-preferred enzyme, while Aly44Pa was an M-specific alginate lyase. Both enzymes degraded alginate in a random endo-acting manner, and the product distribution of Aly44An exhibited a lower degree of polymerization. The characterization of enzymes with different properties in the PL44 family would facilitate the research and application of alginate lyases.