Lata Madhu, Ramya T N C
CSIR- Institute of Microbial Technology, Sector 39-A, Chandigarh, 160036, India.
Academy of Scientific & Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh, 201002, India.
Biochem Biophys Rep. 2024 Jul 19;39:101791. doi: 10.1016/j.bbrep.2024.101791. eCollection 2024 Sep.
Sialidases catalyze the removal of terminal sialic acids from sialylated biomolecules, and their substrate preference is frequently indicated in terms of the glycosidic linkages cleaved (α2-3, α2-6, and α2-8) without mention of the remaining sub-terminal reducing-end saccharide moieties. Many human gut commensal and pathogenic bacteria secrete sialidases to forage for sialic acids, which are then utilized as an energy source or assimilated into membrane/capsular structural components. Infant gut commensals similarly utilize sialylated human milk oligosaccharides containing different glycosidic linkages. Here, we have studied the preference of the bacterial sialidases, BbSia2 from , CpNanI from , and HpNanH from for the glycosidic linkages, Siaα2-3Gal, Siaα2-6Gal, and Siaα2-6GlcNAc, by employing 2-Aminobenzamide-labeled human milk oligosaccharides, 3'-Sialyllactose (3'-SL), 6'-Sialyllactose (6'-SL), and Sialyllacto-N-tetraose-b (LSTb), respectively, as proxies for these glycosidic linkages. BbSia2, NanI, and HpNanH hydrolyzed these three oligosaccharides with the glycosidic linkage preferences, 3-SL (Siaα2-3Gal) ≥ LSTb (Siaα2-6GlcNAc) ≥ 6-SL (Siaα2-6Gal), 3-SL (Siaα2-3Gal) ≥ 6-SL (Siaα2-6Gal) > LSTb (Siaα2-6GlcNAc), and 3'-SL (Siaα2-3Gal) ≥ 6'-SL (Siaα2-6Gal) > LSTb (Siaα2-6GlcNAc), respectively. Our finding suggests that sub-terminal reducing-end saccharide moieties can profoundly influence the substrate preference of sialidases, and advocates for the characterization and indication of the substrate preference of sialidases in terms of both the glycosidic linkage and the sub-terminal reducing-end saccharide moiety.
唾液酸酶催化从唾液酸化生物分子中去除末端唾液酸，其底物偏好通常根据被切割的糖苷键（α2-3、α2-6和α2-8）来表示，而未提及剩余的亚末端还原端糖部分。许多人类肠道共生菌和病原菌分泌唾液酸酶来获取唾液酸，唾液酸随后被用作能量来源或被同化到膜/荚膜结构成分中。婴儿肠道共生菌同样利用含有不同糖苷键的唾液酸化人乳寡糖。在这里，我们通过分别使用2-氨基苯甲酰胺标记的人乳寡糖、3'-唾液酸乳糖（3'-SL）、6'-唾液酸乳糖（6'-SL）和唾液酸乳糖-N-四糖-b（LSTb）作为这些糖苷键的替代物，研究了来自[具体细菌名称1]的BbSia2、来自[具体细菌名称2]的CpNanI和来自[具体细菌名称3]的HpNanH这三种细菌唾液酸酶对糖苷键Siaα2-3Gal、Siaα2-6Gal和Siaα2-6GlcNAc的偏好。BbSia2、NanI和HpNanH分别以3-SL（Siaα2-3Gal）≥LSTb（Siaα2-6GlcNAc）≥6-SL（Siaα2-6Gal）、3-SL（Siaα2-3Gal）≥6-SL（Siaα2-6Gal）>LSTb（Siaα2-6GlcNAc）和3'-SL（Siaα2-3Gal）≥6'-SL（Siaα2-6Gal）>LSTb（Siaα2-6GlcNAc）的糖苷键偏好水解这三种寡糖。我们的发现表明，亚末端还原端糖部分可以深刻影响唾液酸酶的底物偏好，并主张从糖苷键和亚末端还原端糖部分两方面对唾液酸酶的底物偏好进行表征和说明。
