The α-diglucoside trehalose has historically been known as a component of the bacterial stress response, though it more recently has been studied for its relevance in human gut health and biotechnology development. The utilization of trehalose as a nutrient source by bacteria relies on carbohydrate-active enzymes, specifically those of the glycoside hydrolase family 37 (GH37), to degrade the disaccharide into substituent glucose moieties for entry into metabolism. Environmental bacteria using oligosaccharides for nutrients often possess multiple carbohydrate-active enzymes predicted to have the same biochemical activity and therefore are thought to be functionally redundant. In this study, we characterized trehalose degradation by the biotechnologically important saprophytic bacterium Cellvibrio japonicus. This bacterium possesses two predicted α-α-trehalase genes, tre37A and tre37B, and our investigation using mutational analysis found that only the former is essential for trehalose utilization by C. japonicus. Heterologous expression experiments found that only the expression of the C. japonicus tre37A gene in an Escherichia coli treA mutant strain allowed for full utilization of trehalose. Biochemical characterization of C. japonicus GH37 activity determined that the tre37A gene product is solely responsible for cleaving trehalose and is an acidic α-α-trehalase. Bioinformatic and mutational analyses indicate that Tre37A directly cleaves trehalose to glucose in the periplasm, as C. japonicus does not possess a phosphotransferase system. This study facilitates the development of a comprehensive metabolic model for α-linked disaccharides in C. japonicus and more broadly expands our understanding of the strategies that saprophytic bacteria employ to capture diverse carbohydrates from the environment.

中文翻译：

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日本细胞弧菌中的海藻糖降解没有功能上的冗余，仅依赖于Tre37A酶。

历史上，α-二葡萄糖苷海藻糖一直被认为是细菌应激反应的一个组成部分，尽管最近由于其与人类肠道健康和生物技术发展的相关性而进行了研究。细菌利用海藻糖作为营养源依赖于碳水化合物活性酶，特别是糖苷水解酶家族37（GH37）的酶，可将二糖降解为取代糖基，从而进入代谢。使用寡糖作为营养物质的环境细菌通常拥有多种碳水化合物活性酶，这些酶预计具有相同的生化活性，因此被认为在功能上是多余的。在这项研究中，我们通过生物技术上重要的腐生细菌Cellvibrio japonicus表征了海藻糖的降解。该细菌具有两个预测的α-α-海藻糖酶基因tre37A和tre37B，我们使用突变分析的研究发现，只有前者对于日本血吸虫利用海藻糖至关重要。异源表达实验发现，在大肠杆菌treA突变菌株中，只有日本血吸虫tre37A基因的表达 才能充分利用海藻糖。日本血吸虫GH37活性的生化特征确定了tre37A基因产物仅负责切割海藻糖，并且是酸性α-α-海藻糖酶。生物信息学和突变分析表明，Tre37A直接将海藻糖裂解为周质中的葡萄糖，因为日本血吸虫没有磷酸转移酶系统。这项研究促进了日本血吸虫中α-连接的二糖的综合代谢模型的开发，并且更广泛地扩展了我们对腐生细菌用于从环境中捕获多种碳水化合物的策略的理解。