Identification and characterization of a critical loop for the high activity of alginate lyase VaAly2 from the PL7_5 subfamily

Identification and Characterization of a Novel Alginate Lyase VSAly7C with Potential Application for Alginate Di- and Tri-Saccharide Preparation

Brown algae are the largest-producing macroalgae, and alginate lyase plays a key role in the green degradation and high-value conversion of brown algae. This study characterized a novel alginate lyase, VSAly7C, from the marine bacterium Vibrio sp. 8-14, which belongs to the PL7_5 subfamily. Biochemical analysis suggested that VSAly7C is medium-temperature, neutral, and polyG-preferred, with enzyme activities of 2608.3 ± 27.3, 1453.2 ± 50.2, and 2545.2 ± 13.2 U/mg toward polyG, polyM, and sodium alginate, respectively. The minimal oligosaccharides VSAly7C could degrade were tetrasaccharides, and its major products were disaccharides and trisaccharides. Structural bioinformatic analysis of the VSAly7C active groove showed that the -1 to +3 subsite interaction network is crucial for determining the minimal oligosaccharides it can degrade. This study elucidates the catalytic properties, modes of action, and substrate recognition mechanisms of a novel alginate lyase, VSAly7C, which may be potentially applicable in alginate disaccharide and trisaccharide preparation.

Multi-Functional Alginate Lyase AlgVR7 from Vibrio rumoiensis: Structural Insights and Catalytic Mechanisms

In this study, we identified AlgVR7, a novel bifunctional alginate lyase from Vibrio rumoiensis and characterized its biochemical properties and substrate specificity. Sequence alignment analysis inferred the key residues K267, H162, N86, E189, and T244 for AlgVR7 catalysis, and it is derived from the PL7 family; exhibited high activity towards sodium alginate, polyM (PM), and polyG (PG); and can also degrade polygalacturonic acid (PGA) efficiently, with the highest affinity and catalytic efficiency for the MG block of the substrate. The optimal temperature and pH for AlgVR7 were determined to be 40 °C and pH 8, respectively. The enzyme activity of AlgVR7 was maximum at 40 °C, 40% of the enzyme activity was retained after incubation at 60 °C for 60 min, and enzyme activity was still present after 60 min incubation. AlgVR7 activity was stimulated by 100 Mm NaCl, indicating a halophilic nature and suitability for marine environments. Degradation products analyzed using ESI-MS revealed that the enzyme primarily produced trisaccharides and tetrasaccharides. At 40 °C and pH 8.0, its Km values for sodium alginate, PM, and PG were 16.67 μmol, 13.12 μmol, and 22.86 μmol, respectively. Structural analysis and molecular docking studies unveiled the key catalytic residues involved in substrate recognition and interaction. Glu167 was identified as a critical residue for the PL7_5 subfamily, uniquely playing an essential role in alginate decomposition. Overall, AlgVR7 exhibits great potential as a powerful bifunctional enzyme for the efficient preparation of alginate oligosaccharides, with promising applications in biotechnology and industrial fields.

Molecular Engineering of Alginate Lyases and the Potential Agricultural Applications of Their Enzymatic Products

Alginate lyases, enzymes that degrade alginate into unsaturated oligosaccharides, have attracted significant attention for their potential applications across various fields, particularly in agriculture. This review focuses on the molecular engineering of alginate lyases to enhance their activity, stability, and specificity as well as the agricultural applications of the resulting enzymatic products, known as alginate oligosaccharides (AOS). We start by summarizing the sources and classification of alginate lyases, followed by recent advances in their engineering through directed evolution, rational design, truncation of noncatalytic domains, and conserved domain reconstruction. We then explore the diverse agricultural applications of AOS, including their ability to promote plant growth, to increase the content of active plant components, to extend fruit shelf life, and to enhance plant resistance to abiotic stresses. Furthermore, the potential value of AOS as feed additives and preservatives in shrimp-based products is also assessed. This review will not only lay a solid theoretical foundation but also serve as a catalyst for the innovative development and practical application of high-value enzymatic preparations and utilization of AOS-related products, providing new solutions for sustainable agriculture and the food industry.

A bifunctional endolytic alginate lyase with two different lyase catalytic domains from Vibrio sp. H204

Alginate lyases can fully degrade alginate into various size-defined unsaturated oligosaccharide products by β-elimination. Here, we identified the bifunctional endolytic alginate lyase Aly35 from the marine bacterium Vibrio sp. Strain H204. The enzyme Aly35 is classified into the polysaccharide lyase 7 superfamily and contains two alginate lyase catalytic domains. The relationship and function of the two lyase domains are not well known. Thus, the full-length recombinant enzyme and its truncated proteins Aly35-CD1 (catalytic domain 1), Aly35-CD2 (catalytic domain 2 domain) were constructed. The three enzymes showed similar biochemical characteristics and exhibited temperature and pH stability. Further research showed that Aly35 and Aly35-CD2 can efficiently degrade alginate, polymannuronate (PM) and polyguluronate (PG) into a series of unsaturated oligosaccharides, while Aly35-CD1 exhibits greater PM-degrading activity than that of Aly35-CD2 but can not degraded PG efficiently. The results suggest that the domain (Trp295-His582) is critical for PG-degrading activity, the domain has (Leu53-Lys286) higher PM-degrading activity, both catalytic domains together confer increased alginate (including M-blocks and G blocks)-degrading activity. The enzyme Aly35 and its truncations Aly35-CD1 and Aly35-CD2 will be useful tools for structural analyses and for preparing bioactive oligosaccharides, especially Aly35-CD1 can be used to prepare G unit-rich oligosaccharides from alginate.

Low-cost and efficient strategy for brown algal hydrolysis: Combination of alginate lyase and cellulase

Brown algae are rich in biostimulants that not only stimulate the overall development and growth of plants but also have great beneficial effects on the whole soil-plant system. However, alginate, the major component of brown algae, is comparatively difficult to degrade. The cost of preparing alginate oligosaccharides (AOSs) is still too high to produce seaweed fertilizer. In this work, the marine bacterium Vibrio sp. B1Z05 is found to be capable of efficient alginate depolymerization and harbors an extended pathway for alginate metabolism. The B1Z05 extracellular cell-free supernatant exhibited great potential for AOS production at low cost, which, together with cellulase, can efficiently hydrolyze seaweed. The brown algal hydrolysis rates were significantly greater than those of the commercial alginate lyase product CE201, and the obtained seaweed extracts were rich in phytohormones. This work provides a low-cost but efficient strategy for the sustainable production of desirable AOSs and seaweed fertilizer.