Zhuang Xiaoyan, Jiao Chao, Guo Zewang, Xiao Qiong, Chen Jun, Chen Fuquan, Yang Qiuming, Ru Yi, Weng Huifen, Wang Siyuan, Xiao Anfeng, Zhang Yonghui
College of Ocean Food and Biological Engineering, Jimei University, Xiamen 361005, China.
Suzhou Institute for Drug Control, Suzhou 215000, China.
Mar Drugs. 2025 Jun 15;23(6):254. doi: 10.3390/md23060254.
Alginate lyases are critical enzymes in hydrolyzing alginate into alginate oligosaccharides (AOS), which are bioactive compounds known for their antioxidant properties and ability to lower serum glucose and lipid concentrations. However, elucidating catalytic mechanisms and discovering enzymes with enhanced catalytic efficiency remain long-term challenges. Here, we report AlgL2491, a novel bifunctional and cold-adapted alginate lyase from ASY5, belonging to the polysaccharide lyase family 18. This enzyme uniquely cleaves both polyguluronic (polyG) and polymannuronic (polyM), predominantly releasing disaccharides, trisaccharides, and tetrasaccharides after 12 h of hydrolysis. The enzyme achieves peak catalytic efficiency at 35 °C and pH 7.5, with activity increasing 5.5-fold in 0.5 M of NaCl. Molecular dynamics simulations demonstrate that salt ions enhance structural stability by minimizing conformational fluctuations and strengthening interdomain interactions, providing mechanistic insights into its salt-activated behavior. The alginate oligosaccharides (AOS) exhibit excellent free radical-scavenging activities of 86.79 ± 0.31%, 83.42 ± 0.18%, and 71.28 ± 2.27% toward hydroxyl, ABTS, and DPPH radicals, with IC50 values of 8.8, 6.74, and 9.71 mg/mL, respectively. These findings not only reveal the salt-activation mechanism of AlgL2491 and highlight the potential value of its hydrolysate in antioxidant activity but also provide a sustainable industrial solution in industrial-scale AOS production directly from marine biomass, eliminating the need for energy-intensive desalination of alginate, which may inform future biocatalyst design for marine polysaccharide valorization.
海藻酸裂解酶是将海藻酸水解为海藻酸寡糖（AOS）的关键酶，海藻酸寡糖是具有生物活性的化合物，以其抗氧化特性以及降低血清葡萄糖和脂质浓度的能力而闻名。然而，阐明催化机制并发现具有更高催化效率的酶仍然是长期挑战。在此，我们报道了AlgL2491，这是一种来自ASY5的新型双功能且适应低温的海藻酸裂解酶，属于多糖裂解酶家族18。该酶独特地切割聚古洛糖醛酸（polyG）和聚甘露糖醛酸（polyM），水解12小时后主要释放二糖、三糖和四糖。该酶在35°C和pH 7.5时达到最高催化效率，在0.5 M NaCl中活性增加5.5倍。分子动力学模拟表明，盐离子通过最小化构象波动和加强结构域间相互作用来增强结构稳定性，为其盐激活行为提供了机制见解。海藻酸寡糖（AOS）对羟基自由基、ABTS自由基和DPPH自由基表现出优异的自由基清除活性，分别为86.79±0.31%、83.42±0.18%和71.28±2.27%，IC50值分别为8.8、6.74和9.71 mg/mL。这些发现不仅揭示了AlgL2491的盐激活机制，突出了其水解产物在抗氧化活性方面的潜在价值，还为直接从海洋生物质进行工业规模的AOS生产提供了可持续的工业解决方案，无需对海藻酸进行耗能的脱盐处理，这可能为未来海洋多糖增值的生物催化剂设计提供参考。
