Biochemical Properties of a New Polysaccharide Lyase Family 25 Ulvan Lyase TsUly25B from Marine Bacterium Thalassomonas sp. LD5

Improving the thermostability of ulvan lyase from polysaccharide lyase family 25 based on multiple computational rational design strategies

A rational design strategy to improve the thermal stability of enzymes is essential for advancing industrial applications. This study proposes a computer-aided rational design strategy combining deep learning and multiple energy function methods to enhance the thermal stability of ulvan lyase. ColabFold was employed for structure prediction. FoldX, Rosetta, and Schrödinger used to screen mutants for thermal stability. Three single-point mutants, A117V, K145L, and A237V, exhibited significantly enhanced enzyme thermal stability. Further combination of mutations revealed synergistic effects, with the most prominent double mutant A117V/A237V showing a half-life of 31.11 min, extending by 8.91 and 13.95 min compared to A117V and A237V, respectively. It also showed a 10 °C increase in Tm and retained 5.12-fold residual activity after 30 min of incubation at 40 °C compared to those of wild type, respectively. Molecular dynamics simulations revealed that the A117V/A237V reduced the flexibility of the loop regions and increased the intramolecular hydrogen bonds. Additionally, the A237V exhibited an optimal pH of 10.0, while the double mutants A117V/A237V and K145L/A237V showed a shift to pH 9.0, compared to pH 8.0 for the wild type. This study demonstrates that computer-aided rational design as a promising strategy to improve the thermostability of ulvan lyase.

Advances in structural modification of fucoidans, ulvans, and carrageenans to improve their biological functions for potential therapeutic application

Marine sulfated polysaccharides constitute a class of bioactive polymers commonly found in cell walls of macroalgae. Among these macromolecular substances, fucoidans, ulvans, and carrageenans have attracted considerable attention providing interesting therapeutic properties affected by a combination of various structural factors, such as sulfation pattern, molecular weight, monosaccharide composition, and glycosidic linkages. Remarkably, chemical modification, enzymatic hydrolysis and crosslinking are promising approaches for developing the application of these polysaccharides through enhancement and/or addition of new biological properties. This paper reviews the recent advances on these structure modification methods on fucoidans, ulvans, and carrageenans. The physical, chemical and biological properties influenced by the addition of functional groups are also discussed. In addition, an overview of specific enzymes selectively producing oligosaccharides with improved bioactivities as well as ionic and covalent cross-linking strategies are provided. These targeted methods have the potential to develop novel compounds with outstanding biodegradability and biocompatibility, along with low toxicity suitable for diverse applications in biomedical fields, including drug delivery.

Efficient degradation of the polysaccharide extracted from Enteromorpha prolifera by using a novel polysaccharide lyase family 28 enzyme with high activity

The polysaccharides originated from Enteromorpha species exhibited versatile physiological activities and great potential in food and medicine industries. The oligosaccharides, which prepared from polysaccharide by enzymatic hydrolysis, retained the excellent activity as polysaccharide, and then revealed better solubility, bioavailability and effectiveness. However, there are few reports on Enteromorpha polysaccharide (EP)-degrading enzymes for efficient degradation of EP and high-valued utilization of Enteromorpha biomass. Herein, a novel EP-degrading enzyme, EPD1, was identified and heterologously expressed. It could efficiently hydrolyze the EP with high activity (985.755 U/mg) and exhibited optimal activity at 50 °C and a pH of 10.0. The Km value of EPD1 was 7.5512 mg·mL-1 and the Vmax value was 4.9109 μmol·min-1·mL-1. Furthermore, EPD1 demonstrated cold adaptation as evidenced by minimal activity loss following incubation at temperatures below 30 °C for 1 h. HPLC and ESI-MS analysis revealed that EPD1 could produce disaccharides, trisaccharides and tetrasaccharides as the final degradation products from EPs. In conclusion, a novel EP-degrading enzyme with high activity and excellent performance was identified and it can expand the database of EP-degrading enzymes and provide the possibility to make full use of EPs.

Pseudoalteromonas agarivorans-derived novel ulvan lyase of polysaccharide lyase family 40: Potential application of ulvan and partially hydrolyzed products in cosmetic industry

Ulvan is a complex sulfated polysaccharide in the cell walls of green algae with extensive applications in food, pharmaceutical, and agricultural industries, prompting extensive studies on ulvan, its oligosaccharides, monosaccharides, and cost-effective depolymerization methods. Our primary objectives were to investigate novel ulvan-utilizing marine bacteria, perform recombinant engineering of genes responsible for ulvan depolymerization, and determine their potential industrial applications. Samples were collected from Jeju Island, which is a South Korean region with significant excessive green algal growth, especially that of Ulva species. The marine bacterium Pseudoalteromonas agarivorans efficiently uses ulvan as its primary carbon source, indicating its potential for ulvan degradation. Through whole-genome sequencing the paul40 gene, which is a polysaccharide lyase family 40 (PL40) member, was identified and subsequently engineered into the pET-16b vector for expression as a His-tagged 95 kDa fusion protein. The ulvan depolymerization process was evaluated and confirmed using various analytical techniques including dinitrosalicylic acid assay, thin-layer chromatography, and gel permeation chromatography. Optimal enzyme activity occurred at 35°C, pH 8.0 in phosphate buffer, and 2.5 mM of NaCl. Furthermore, enzyme characterization and specific activity measurements were performed. This study is the first to report hyaluronidase and elastase inhibition by ulvan and its derivatives along with the characterization of an ulvan lyase enzyme from the PL40 family.

ONE-SENTENCE SUMMARY

This study reports the identification and recombinant expression of a novel ulvan-degrading enzyme from Pseudoalteromonas agarivorans, demonstrating its potential for cosmetic industrial applications by revealing ulvan's and partially hydrolyzed ulvan's hyaluronidase and elastase inhibition properties.

Characterisation of High Alkaline-Tolerant Novel Ulvan Lyase from Pseudoalteromonas agarivorans: Potential Applications of Enzyme Derived Oligo-Ulvan as Anti-Diabetic Agent

Green algae, particularly Ulva species, are rich in complex polysaccharides, such as ulvan, which have significant potential for biotechnological applications. However, the biochemical properties of ulvan depolymerised products remain underexplored. The enzymatic depolymerisation of ulvan has garnered attention owing to its cost advantages over alternative methods. Nevertheless, the biochemical characterisation of ulvan lyases, specifically those belonging to the polysaccharide lyase family 25 (PL25), is limited. In this study, we identified and biochemically characterised a novel PL25 ulvan lyase, PaUL25, which functions optimally at pH 10. Additionally, we explored the alpha (α)-glucosidase inhibitory properties of ulvan depolymerised products. PaUL25 exhibited optimum activity at 35 °C in Tris-HCl buffer (pH 10). Moreover, enzyme activity was enhanced by more than 150% in the presence of Mn2+ metal ions at and below concentrations of 10 mM. The endolytic action of PaUL25 produced ulvan oligosaccharides with degrees of polymerisation of 2 and 4 as its end products. Partially and completely hydrolysed ulvan oligosaccharides exhibited α-glucosidase inhibitory activity, with half inhibitory concentration IC50 values of 3.21 ± 0.13 and 2.51 ± 0.19 mg/mL, respectively. These findings expand our understanding of PL25 and highlight the pharmaceutical potential of ulvan oligosaccharides, particularly as antidiabetic agents.

Directed preparation of algal oligosaccharides with specific structures by algal polysaccharide degrading enzymes

Seaweed polysaccharides have a wide range of sources and rich content, with various biological activities such as anti-inflammatory, anti-tumor, anticoagulant, and blood pressure lowering. They can be applied in fields such as food, agriculture, and medicine. However, the poor solubility of macromolecular seaweed polysaccharides limits their further application. Reports have shown that some biological activities of seaweed oligosaccharides are more extensive and superior to that of seaweed polysaccharides. Therefore, reducing the degree of polymerization of polysaccharides will be the key to the high value utilization of seaweed polysaccharide resources. There are three main methods for degrading algal polysaccharides into algal oligosaccharides, physical, chemical and enzymatic degradation. Among them, enzymatic degradation has been a hot research topic in recent years. Various types of algal polysaccharide hydrolases and related glycosidases are powerful tools for the preparation of algal oligosaccharides, including α-agarases, β-agaroses, α-neoagarose hydrolases and β-galactosidases that are related to agar, κ-carrageenases, ι-carrageenases and λ-carrageenases that are related to carrageenan, β-porphyranases that are related to porphyran, funoran hydrolases that are related to funoran, alginate lyases that are related to alginate and ulvan lyases related to ulvan. This paper describes the bioactivities of agar oligosaccharide, carrageenan oligosaccharide, porphyran oligosaccharide, funoran oligosaccharide, alginate oligosaccharide and ulvan oligosaccharide and provides a detailed review of the progress of research on the enzymatic preparation of these six oligosaccharides. At the same time, the problems and challenges faced are presented to guide and improve the preparation and application of algal oligosaccharides in the future.

Polysaccharides and oligosaccharides originated from green algae: structure, extraction, purification, activity and applications

With the proceeding of global warming and water eutrophication, the phenomenon of green tide has garnered significant societal interest. Consequently, researchers had increasingly focused on the potential applications of green algae biomass, particularly its polysaccharides. The polysaccharide serves as the primary active constituent of green algae and has demonstrated numerous advantageous biological activities, including antioxidant, antiviral, anticoagulant, hypolipidemic and immuno-modulatory activities. The favorable bioavailability and solubility of green algae oligosaccharides are attributed to their low molecular weight. So there has been a growing interest in researching green algae polysaccharides and oligosaccharides for the utilization of marine biological resources. This review summarized the extraction, purification, chemical structure, composition, biological activity, and potential applications prospect of polysaccharides and oligosaccharides derived from green algae. The review could be helpful for expanding the applications of polysaccharides and oligosaccharides of green algae.

Biochemical Characterization of a Novel Thermostable Ulvan Lyase from Tamlana fucoidanivorans CW2-9

Ulvan is a complex sulfated polysaccharide extracted from Ulva, and ulvan lyases can degrade ulvan through a β-elimination mechanism to obtain oligosaccharides. In this study, a new ulvan lyase, EPL15085, which belongs to the polysaccharide lyase (PL) 28 family from Tamlana fucoidanivorans CW2-9, was characterized in detail. The optimal pH and salinity are 9.0 and 0.4 M NaCl, respectively. The Km and Vmax of recombinant EPL15085 toward ulvan are 0.80 mg·mL-1 and 11.22 μmol·min -1 mg-1·mL-1, respectively. Unexpectedly, it is very resistant to high temperatures. After treatment at 100 °C, EPL15085 maintained its ability to degrade ulvan. Molecular dynamics simulation analysis and site-directed mutagenesis analysis indicated that the strong rigidity of the disulfide bond between Cys74-Cys102 in the N-terminus is related to its thermostability. In addition, oligosaccharides with disaccharides and tetrasaccharides were the end products of EPL15085. Based on molecular docking and site-directed mutagenesis analysis, Tyr177 and Leu134 are considered to be the crucial residues for enzyme activity. In conclusion, our study identified a new PL28 family of ulvan lyases, EPL15085, with excellent heat resistance that can expand the database of ulvan lyases and provide the possibility to make full use of ulvan.

Biochemical characterisation of a PL24 ulvan lyase from seaweed-associated Vibrio sp. FNV38

Ulvan is a green macroalgal cell wall polysaccharide that has tremendous potential for valorisation due to its unique composition of sulphated rhamnose, glucuronic acid, iduronic acid and xylose. Several potential applications such as production of biofuels, bioplastics and other value-added products necessitate the breakdown of the polysaccharide to oligomers or monomers. Research on ulvan saccharifying enzymes has been continually increasing over the last decade, with the increasing focus on valorisation of seaweed biomass for a biobased economy. Lyases are the first of several enzymes that are involved in saccharifying the polysaccharide and several ulvan lyases have been structurally and biochemically characterised to enable their effective use in the valorisation processes. This study investigates the whole genome of Vibrio sp. FNV38, an ulvan metabolising organism and biochemical characteristics of a PL24 ulvan lyase that it possesses. The genome of Vibrio sp. FNV38 has a diverse CAZy profile with several genes involved in the metabolism of ulvan, cellulose, agar, and alginate. The enzyme exhibits optimal activity at pH 8.5 in 100 mM Tris-HCl buffer and 30 °C. However, its thermal stability is poor with significant loss of activity after 2 h of incubation at temperatures above 25 °C. Breakdown product analysis reveals that the enzyme depolymerised the polysaccharide predominantly to disaccharides and tetrasaccharides.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10811-023-03136-3.

Biochemical characterization of a new ulvan lyase and its applicability in utilization of ulvan and preparation of ulva oligosaccharides

Ulva is globally distributed specie and has a high economic value. Ulvan is one of the main active substances in Ulva, which has a variety of biological properties. Ulvan lyase degrades ulvan through a β-elimination mechanism which cleaves the β-glycosidic bond between Rha3S and GlcA or IdoA. The complex monosaccharide composition of ulvan makes it promising for use in food and pharmaceutical applications. This thesis explores a putative ulvan lyase from Alteromonas sp. KUL_42. We expressed and purified the protein, performed a series of characterizations and signal peptide had been removed. The results showed that the protein molecular weight of ULA-2 was 53.97 kDa, and it had the highest catalytic activity at 45 °C and pH 8.0 in Tris-HCl buffer. The Km and Vmax values were 2.24 mg · mL-1 and 2.048 μmol · min-1 · mL-1, respectively. The activity of ULA-2 was able to maintain more than 80% at 20 ~ 30 °C. ESI-MS analysis showed that the primary end-products were mainly disaccharides to tetrasaccharides. The study of ULA-2 enriches the ulvan lyase library, promotes the development and high-value utilization of Ulva resources, and facilitates further research applications of ulvan lyase in ulva oligosaccharides.

Ulvan and Ulva oligosaccharides: a systematic review of structure, preparation, biological activities and applications

Ulva is one of the main green algae causing green tide disasters. Ulvan is the primarily component polysaccharide of the cell wall of Ulva and its complex structure and monosaccharide composition resulted in various biological activities. However, the high-value and effective utilization of extracted ulvan have been obstructed by limitations ranging from large molecular weight and low solubility to poor bioavailability. Ulva oligosaccharide obtained by degrading ulvan can not only ideally retain the various biological activities of ulvan very well but also effectively solve the problems of low solubility and poor bioavailability. The preparation and biological activity studies of ulvan and Ulva oligosaccharides have become a hot spot in the field of marine biological resources development research. At present, the comprehensive reviews of ulvan and Ulva oligosaccharides are still scarce. What are overviewed in this paper are the chemical composition, structure, extraction, and purification of ulvan and Ulva oligosaccharides, where research progress on the biological activities of ulvan and Ulva oligosaccharides is summarized and prospected. A theoretical and practical basis has been provided for further research on ulvan and Ulva oligosaccharides, as well as the high-value development and effective utilization of marine algae resources.