Recombinant Expression of κ-Carrageenase Cgk483 from Photobacterium rosenbergii and in Vitro Lipid-Lowering Activity of κ-Carrageenan Oligosaccharides Prepared Using It

This study aimed to explore the recombinant expression of κ-carrageenase Cgk483 from Photobacterium rosenbergii and its application in preparing carrageenan oligosaccharides, which were structurally characterized and evaluated for in vitro hypolipidemic effects. Through gene cloning and heterologous expression, the electrophoretically pure recombinant enzyme Cgk483 was successfully obtained, with a molecular mass of 35.89 kDa and its specific activity was 489.88 U/mg, which was approximately 10 times higher than that of the wild-type enzyme. Enzyme kinetics studies showed that the optimal reaction temperature and pH for Cgk483 were 40 ℃ and 8.0, respectively. It was stable at temperatures below 40 ℃ and within the pH range of 5.0-10.0. Fe²⁺, Na⁺, and Ba²⁺ were found to enhance the enzyme activity. Using the recombinant enzyme Cgk483, κ-carrageenan oligosaccharides consisting of disaccharide, tetrasaccharide and hexasaccharide were successfully prepared. Structural analysis indicated that the enzymatic hydrolysis did not disrupt the main chain but resulted in the exposure of hydroxyl and other groups, improving the solubility of κ-carrageenan oligosaccharides. In vitro hypolipidemic assay demonstrated that κ-carrageenan oligosaccharides significantly inhibited oxidized low-density lipoprotein (Ox-LDL)-induced foam cell formation in RAW264.7 macrophages, reducing lipid accumulation. This study provides a new idea for the efficient preparation of κ-carrageenan oligosaccharides for use in the prevention and treatment of atherosclerosis.