Characterization of a Novel PolyM-Preferred Alginate Lyase from Marine Vibrio splendidus OU02

Abstract

Alginate lyases are enzymes that degrade alginate into oligosaccharides which possess a variety of biological activities. Discovering and characterizing novel alginate lyases has great significance for industrial and medical applications. In this study, we reported a novel alginate lyase, AlyA-OU02, derived from the marine Vibrio splendidus OU02. The BLASTP searches showed that AlyA-OU02 belonged to polysaccharide lyase family 7 (PL7) and contained two consecutive PL7 domains, which was rare among the alginate lyases in PL7 family. Both the two domains, AlyAa and AlyAb, had lyase activities, while AlyAa exhibited polyM preference, and AlyAb was polyG-preferred. In addition, the enzyme activity of AlyAa was much higher than AlyAb at 25 °C. The full-length enzyme of AlyA-OU02 showed polyM preference, which was the same as AlyAa. AlyAa degraded alginate into di-, tri-, and tetra-alginate oligosaccharides, while AlyAb degraded alginate into tri-, tetra-, and penta-alginate oligosaccharides. The degraded products of AlyA-OU02 were similar to AlyAa. Our work provided a potential candidate in the application of alginate oligosaccharide production and the characterization of the two domains might provide insights into the use of alginate of this organism.

Purification and Characterization of a Novel Endolytic Alginate Lyase from Microbulbifer sp. SH-1 and Its Agricultural Application

“…AlgSH7 contains an QIH sequence, while, it prefers polyM blocks. This result is similar to AlyA-OU02, AlyPM, and FlAlyA [24][25][26]. Most of the reported PL7 family alginate lyases have endolytic activity.…”

“…Alginate lyases vary in substrate specificities, and they are commonly assigned to G-specific, M-specific, and bifunctional groups [11]. The conserved amino acids play vital roles in catalyzing reaction or forming jelly roll β-sandwich structure, which is regarded as a binding site of a suitable substrate [24,34]. It has been reported that the conserved regions of polyM-preference, polyG-preference, and polyMG-preference alginate lyases contain QVH, QIH, and QIH amino acid residues, respectively [24].…”

“…The conserved amino acids play vital roles in catalyzing reaction or forming jelly roll β-sandwich structure, which is regarded as a binding site of a suitable substrate [24,34]. It has been reported that the conserved regions of polyM-preference, polyG-preference, and polyMG-preference alginate lyases contain QVH, QIH, and QIH amino acid residues, respectively [24]. For example, AlgNJU-03, AlgM4, and AlyPI contain QIH in the conserved region and show activities towards polyM and polyG [21,34,35].…”

“…These results indicated that the substrate specificity of AlgSH7 is polyM-specific, and the reaction pattern of AlgSH7 may be endolytic mode. The substrate specificities of PL7 alginate lyases are related to the amino acid sequence in the conserved regions, which formed the cavity structure to bind to suitable substrates [24]. Recent studies have declared that polyM-specific, polyG-specific, and polyMG-specific alginate lyases contained QVH, QIH, and QIH in the conserved regions, respectively [8].…”

“…However, AlgSH7 is contrary to this accepted rule. AlgSH7 is active towards polyM, containing the QIH sequence which is similar to AlyA-OU02 [24], AlyPM [25], and FlAlyA [26].…”