Ulvan polysaccharide-degrading enzymes: An updated and comprehensive review of sources category, property, structure, and applications of ulvan lyases

Ulvan, extracted from the marine green algae belonging to the genus Ulva, is mainly composed of four monosaccharides consisting of rhamnose, xylose, glucuronic acid and iduronic acid. It has great potential in the fields of food, pharmaceuticals and chemistry. It can be degraded by ulvan lyase with a β-elimination mechanism, which cleaves the β-glycosidic bond between sulfated rhamnose and glucuronic acid/iduronic acid, thereby producing an Ulva oligosaccharide with unsaturated bond. These oligosaccharides have several pleasing functions, including antioxidant, antiviral, antilipidic, antibacterial, and other effects. The latest CAZy data shows that ulvan lyases are composed of four families of lyases: PL24, PL25, PL28, and PL40. The structural features of some enzymes have been fully demonstrated, which is highly helpful in understanding their catalytic mechanisms. This review summarizes key sources, classifications, and key research advances in the biochemical properties of enzymes. In addition, its structural features and catalytic mechanism have been organized. Finally, we briefly summarized the potential of various active functional oligosaccharides produced by degrading ulvan in future applications. This detailed information can give us a better understanding of ulvan.