The availability and repartition of fucosylated glycans within the gastrointestinal tract contributes to the adaptation of gut bacteria species to ecological niches. To access this source of nutrients, gut bacteria encode α-L-fucosidases (fucosidases) which catalyze the hydrolysis of terminal α-L-fucosidic linkages. We determined the substrate and linkage specificities of fucosidases from the human gut symbiont Ruminococcus gnavus. Sequence similarity network identified strain-specific fucosidases in R. gnavus ATCC 29149 and E1 strains that were further validated enzymatically against a range of defined oligosaccharides and glycoconjugates. Using a combination of glycan microarrays, mass spectrometry, isothermal titration calorimetry, crystallographic and saturation transfer difference NMR approaches, we identified a fucosidase with the capacity to recognize sialic acid-terminated fucosylated glycans (sialyl Lewis X/A epitopes) and hydrolyze α1-3/4 fucosyl linkages in these substrates without the need to remove sialic acid. Molecular dynamics simulation and docking showed that 3'-Sialyl Lewis X (sLeX) could be accommodated within the binding site of the enzyme. This specificity may contribute to the adaptation of R. gnavus strains to the infant and adult gut and has potential applications in diagnostic glycomic assays for diabetes and certain cancers.

中文翻译：

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来自人类肠道共生菌 Ruminococcus gnavus 的岩藻糖苷酶。

胃肠道内岩藻糖基化聚糖的可用性和重新分配有助于肠道细菌物种适应生态位。为了获得这种营养来源，肠道细菌编码 α-L-岩藻糖苷酶（岩藻糖苷酶），催化末端 α-L-岩藻糖苷键的水解。我们确定了来自人类肠道共生体 Ruminococcus gnavus 的岩藻糖苷酶的底物和连锁特异性。序列相似性网络在 R. gnavus ATCC 29149 和 E1 菌株中鉴定了菌株特异性岩藻糖苷酶，这些酶进一步针对一系列定义的寡糖和糖缀合物进行了酶促验证。使用聚糖微阵列、质谱、等温滴定量热法、晶体学和饱和转移差异核磁共振方法的组合，我们鉴定了一种岩藻糖苷酶，它能够识别唾液酸封端的岩藻糖基化聚糖（唾液酸路易斯 X/A 表位）并水解这些底物中的 α1-3/4 岩藻糖基键，而无需去除唾液酸。分子动力学模拟和对接表明 3'-Sialyl Lewis X (sLeX) 可以容纳在酶的结合位点内。这种特异性可能有助于 R. gnavus 菌株适应婴儿和成人肠道，并在糖尿病和某些癌症的诊断糖组学检测中具有潜在应用。-Sialyl Lewis X (sLeX) 可以容纳在酶的结合位点内。这种特异性可能有助于 R. gnavus 菌株适应婴儿和成人肠道，并在糖尿病和某些癌症的诊断糖组学检测中具有潜在应用。-Sialyl Lewis X (sLeX) 可以容纳在酶的结合位点内。这种特异性可能有助于 R. gnavus 菌株适应婴儿和成人肠道，并在糖尿病和某些癌症的诊断糖组学检测中具有潜在应用。