Arabinoxylan hydrolysates (AXH) are the hydrolyzed products of the major components of the dietary fiber arabinoxylan. AXH include diverse oligosaccharides varying in xylose polymerization and side residue modifications with arabinose at the O-2 and/or O-3 position of the xylose unit. Previous studies have reported that AXH exhibit prebiotic properties on gut bifidobacteria; moreover, several adult-associated bifidobacterial species (e.g., Bifidobacterium adolescentis and Bifidobacterium longum subsp. longum) are known to utilize AXH. In this study, we tried to elucidate the molecular mechanisms of AXH utilization by Bifidobacterium pseudocatenulatum, which is a common bifidobacterial species found in adult feces. We performed transcriptomic analysis of B. pseudocatenulatum YIT 4072^T, which identified three upregulated gene clusters during AXH utilization. The gene clusters encoded three sets of ATP-binding cassette (ABC) transporters and five enzymes belonging to glycoside hydrolase family 43 (GH43). By characterizing the recombinant proteins, we found that three solute-binding proteins of ABC transporters showed either broad or narrow specificity, two arabinofuranosidases hydrolyzed either single- or double-decorated arabinoxylooligosaccharides, and three xylosidases exhibited functionally identical activity. These data collectively suggest that the transporters and glycoside hydrolases, encoded in the three gene clusters, work together to utilize AXH of different sizes and with different side residue modifications. Thus, our study sheds light on the overall picture of how these proteins collaborate for the utilization of AXH in B. pseudocatenulatum and may explain the predominance of this symbiont species in the adult human gut.

中文翻译：

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多个转运蛋白和糖苷水解酶参与假单歧杆菌双歧杆菌衍生的阿拉伯糖木聚糖的利用。

阿拉伯木聚糖水解产物（AXH）是膳食纤维阿拉伯木聚糖主要成分的水解产物。AXH包括在木糖聚合和在木糖单元的O-2和/或O-3位置用阿拉伯糖修饰侧残基的各种低聚糖。先前的研究已经报道AXH对肠道双歧杆菌表现出益生元的特性。此外，若干成人相关的双歧杆菌物种（例如，青春双歧杆菌和长双歧杆菌亚种长双歧杆菌）已知利用AXH。在这项研究中，我们试图阐明假双歧杆菌利用AXH的分子机制。是成年粪便中常见的双歧杆菌种。我们进行了B. pseudocatenulatum YIT 4072 ^T的转录组分析，它在AXH利用过程中确定了三个上调的基因簇。基因簇编码三套ATP结合盒（ABC）转运蛋白和五个糖苷水解酶家族43（GH43）的酶。通过表征重组蛋白，我们发现ABC转运蛋白的三个溶质结合蛋白表现出宽泛或狭窄的特异性，两个阿拉伯呋喃糖苷酶水解了单或双装饰阿拉伯糖低聚糖，而三个木糖苷酶表现出功能相同的活性。这些数据共同表明，在三个基因簇中编码的转运蛋白和糖苷水解酶共同作用以利用不同大小和不同侧残基修饰的AXH。从而，B. pseudocatenulatum，可能解释了这种共生物种在成年人类肠道中的优势。