Catalysis, Structures, and Applications of Carbohydrate Epimerases

Rumen microbiome-driven insight into bile acid metabolism and host metabolic regulation

Gut microbes play a crucial role in transforming primary bile acids (BAs) into secondary forms, which influence systemic metabolic processes. The rumen, a distinctive and critical microbial habitat in ruminants, boasts a diverse array of microbial species with multifaceted metabolic capabilities. There remains a gap in our understanding of BA metabolism within this ecosystem. Herein, through the analysis of 9371 metagenome-assembled genomes and 329 cultured organisms from the rumen, we identified two enzymes integral to BA metabolism: 3-dehydro-bile acid delta4,6-reductase (baiN) and the bile acid:Na + symporter family (BASS). Both in vitro and in vivo experiments were employed by introducing exogenous BAs. We revealed a transformation of BAs in rumen and found an enzyme cluster, including L-ribulose-5-phosphate 3-epimerase and dihydroorotate dehydrogenase. This cluster, distinct from the previously known BA-inducible operon responsible for 7α-dehydroxylation, suggests a previously unrecognized pathway potentially converting primary BAs into secondary BAs. Moreover, our in vivo experiments indicated that microbial BA administration in the rumen can modulate amino acid and lipid metabolism, with systemic impacts underscored by core secondary BAs and their metabolites. Our study provides insights into the rumen microbiome's role in BA metabolism, revealing a complex microbial pathway for BA biotransformation and its subsequent effect on host metabolic pathways, including those for glucose, amino acids, and lipids. This research not only advances our understanding of microbial BA metabolism but also underscores its wider implications for metabolic regulation, offering opportunities for improving animal and potentially human health.

Isomerase and epimerase: overview and practical application in production of functional sugars

The biosynthesis of functional sugars has gained significant attention due to their potential health benefits and increasing demand in the food industry. Enzymatic synthesis has emerged as a promising approach, offering high catalytic efficiency, chemoselectivity, and stereoselectivity. However, challenges such as poor thermostability, low catalytic efficiency, and food safety concerns have limited the commercial production of functional sugars. Protein engineering, including directed evolution and rational design, has shown promise in overcoming these barriers and improving biocatalysts for large-scale production. Furthermore, enzyme immobilization has proven effective in reducing costs and facilitating the production of functional sugars. To ensure food safety, the use of food-grade expression systems has been explored. However, downstream technologies, including separation, purification, and crystallization, still pose challenges in terms of efficiency and cost-effectiveness. Addressing these challenges is crucial to optimize the overall production process. Despite the obstacles, the future outlook for functional sugars is promising, driven by increasing awareness of their health benefits and continuous technological advancements. With further research and technological breakthroughs, industrial-scale production of functional sugars through biosynthesis will become a reality, leading to their widespread incorporation in various industries and products.