Abstract

Seaweeds have received considerable attention as sources of dietary fiber and biomass for manufacturing valuable products. The major polysaccharides of red seaweeds include agar and porphyran. In a marine environment, marine bacteria utilize agar and porphyran through the agarase and porphyranase genes encoded in their genomes. Most of these enzymes identified and characterized so far originate from marine bacteria. Recently, Bacteroides plebeius, a human gut bacterium isolated from seaweed-eating Japanese individuals, was revealed to contain a polysaccharide utilization locus (PUL) targeting the porphyran and agarose of red seaweeds. For example, B. plebeius contains an endo-type β-agarase, BpGH16A, belonging to glycoside hydrolase family 16. BpGH16A cleaves the β-1,4-glycosidic linkages of agarose and produces neoagarooligosccharides from agarose. Since it is crucial to study the characteristics of BpGH16A to understand the depolymerization pathway of red seaweed polysaccharides by B. plebeius in the human gut and to industrially apply the enzyme for the depolymerization of agar, we characterized BpGH16A for the first time. According to our results, BpGH16A is an extracellular endo-type β-agarase with an optimal temperature of 40 °C and an optimal pH of 7.0, which correspond to the temperature and pH of the human colon. BpGH16A depolymerizes agarose into neoagarotetraose (as the main product) and neoagarobiose (as the minor product). Thus, BpGH16A is suggested to be an important enzyme that initiates the depolymerization of red seaweed agarose or agar in the human gut by B. plebeius.

Key points

• Bacteroides plebeius is a human gut bacterium isolated from seaweed-eating humans.

• BpGH16A is an extracellular endo-type β-agarase with optimal conditions of 40 °C and pH 7.0.

• BpGH16A depolymerizes agarose into neoagarotetraose and neoagarobiose.

中文翻译：

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Bpleeroides plebeius细菌Bp GH16A的表征，Bp GH16A是引发人体肠道琼脂糖解聚的关键酶

摘要

海藻作为生产有价值产品的膳食纤维和生物质的来源受到了广泛的关注。红海藻的主要多糖包括琼脂和卟啉。在海洋环境中，海洋细菌通过其基因组中编码的琼脂酶和卟啉酶基因利用琼脂和卟啉。到目前为止，已鉴定和表征的大多数酶都来自海洋细菌。最近，从食用海藻的日本人中分离出的人类肠道细菌白骨杆菌（Bacteroides plebeius）被发现含有针对红海藻的卟啉和琼脂糖的多糖利用位点（PUL）。例如，B. plebeius含有内切型β琼脂糖酶，BP GH16A，属于糖苷水解酶家族16，BPGH16A裂解琼脂糖的β-1,4-糖苷键，并从琼脂糖中产生新的琼脂糖寡糖。由于研究Bp GH16A的特性对于了解人双歧杆菌在人肠道中对红海藻多糖的解聚途径以及在工业上将酶用于琼脂解聚至关重要，因此我们首次对Bp GH16A进行了表征。根据我们的结果，Bp GH16A是一种胞外内切型β-琼脂糖酶，最适温度为40°C，最适pH值为7.0，与人结肠的温度和pH值相对应。Bp GH16A将琼脂糖解聚为新琼脂四糖（主要产品）和新琼脂糖（次要产品）。从而，bp的GH16A建议是一个重要的酶发起红海藻中由人体肠道的解聚琼脂糖或琼脂B. plebeius。

关键点

• pleactius plebeius细菌是一种食人海藻的人类肠道细菌。

• BpGH16A是一种胞外内切型β-琼脂糖酶，最佳条件是40°C和pH 7.0。

• BpGH16A将琼脂糖解聚为新琼脂四糖和新琼脂糖。