Abstract：
κ-Carrageenase plays an important role in achieving the high-value utilization of carrageenan. Factors such as the reaction temperature, thermal stability, catalytic efficiency, and product composition are key considerations for its large-scale application. Previous studies have shown that the C-terminal noncatalytic domains (nonCDs) could influence the enzymatic properties, of κ-carrageenases, providing a strategy for exploring κ-carrageenases with different properties, especially catalytic products. Accordingly, two κ-carrageenases (CaKC16A and CaKC16B), from the Catenovulum agarivorans DS2, were selected and further characterized. Bioinformatics analysis suggested that CaKC16A contained a nonCD but CaKC16B did not. CaKC16A exhibited better enzymatic properties than CaKC16B, including thermal stability, substrate affinity, and catalytic efficiency. After truncation of the nonCD of CaKC16A, its thermal stability, substrate affinity, and catalytic efficiency have significantly decreased, indicating the vital role of nonCD in maintaining a good enzymatic property. Moreover, CaKC16A degraded κ-carrageenan to produce a highly single κ-neocarratetrose, while CaKC16B produced a single κ-neocarrabiose. CaKC16A could degrade β/κ-carrageenan to produce a highly single desulfated κ-neocarrahexaose, while CaKC16B produced κ-neocarrabiose and desulfated κ-neocarratetrose. Furthermore, it was proposed that CaKC16A and CaKC16B participate in the B/KC metabolic pathway and serve different roles, providing new insight into obtaining κ-carrageenases with different properties.
摘要：
κ-角叉菜酶在实现角叉菜胶的高值化利用中起着重要作用。反应温度等因素,热稳定性，催化效率，和产品组成是其大规模应用的关键考虑因素。以前的研究表明，C末端非催化结构域（非CD）可以影响酶的性质，κ-角叉菜酶，提供了一种探索具有不同性质的κ-角叉菜胶酶的策略，尤其是催化产品。因此，两种κ-角叉菜胶酶（CaKC16A和CaKC16B），从合排卵agarivoransDS2中选择并进一步表征。生物信息学分析表明，CaKC16A含有非CD，但CaKC16B没有。CaKC16A表现出比CaKC16B更好的酶学性质,包括热稳定性，底物亲和力，和催化效率。在截短CaKC16A的非CD后，它的热稳定性，底物亲和力，催化效率显著下降，表明非CD在保持良好的酶学性质中的重要作用。此外，CaKC16A降解κ-角叉菜胶，产生高度单一的κ-新卡曲酸，而CaKC16B产生单一的κ-新卡拉糖糖。CaKC16A可以降解β/κ-角叉菜胶，产生高度单一的脱硫κ-新六糖，CaKC16B产生κ-新卡那糖和脱硫的κ-新卡那糖。此外，有人提出CaKC16A和CaKC16B参与B/KC代谢途径并发挥不同的作用，为获得具有不同性质的κ-角叉菜胶酶提供了新的见解。
