State Key Laboratory of Animal Nutrition and Feeding, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.
Appl Microbiol Biotechnol. 2024 Apr 8;108(1):289. doi: 10.1007/s00253-024-13131-4.
Rumen microbial urease inhibitors have been proposed for regulating nitrogen emission and improving nitrogen utilization efficiency in ruminant livestock industry. However, studies on plant-derived natural inhibitors of rumen microbial urease are limited. Urease accessory protein UreG, plays a crucial role in facilitating urease maturation, is a new target for design of urease inhibitor. The objective of this study was to select the potential effective inhibitor of rumen microbial urease from major protoberberine alkaloids in Rhizoma Coptidis by targeting UreG. Our results showed that berberine chloride and epiberberine exerted superior inhibition potential than other alkaloids based on GTPase activity study of UreG. Berberine chloride inhibition of UreG was mixed type, while inhibition kinetics type of epiberberine was uncompetitive. Furthermore, epiberberine was found to be more effective than berberine chloride in inhibiting the combination of nickel towards UreG and inducing changes in the second structure of UreG. Molecular modeling provided the rational structural basis for the higher inhibition potential of epiberberine, amino acid residues in G1 motif and G3 motif of UreG formed interactions with D ring of berberine chloride, while interacted with A ring and D ring of epiberberine. We further demonstrated the efficacy of epiberberine in the ruminal microbial fermentation with low ammonia release and urea degradation. In conclusion, our study clearly indicates that epiberberine is a promising candidate as a safe and effective inhibitor of rumen microbial urease and provides an optimal strategy and suitable feed additive for regulating nitrogen excretion in ruminants in the future. KEY POINTS: • Epiberberine is the most effective inhibitor of rumen urease from Rhizoma Coptidis. • Urease accessory protein UreG is an effective target for design of urease inhibitor. • Epiberberine may be used as natural feed additive to reducing NH release in ruminants.
瘤胃微生物脲酶抑制剂被提议用于调节反刍家畜业的氮排放和提高氮利用效率。然而，关于植物来源的天然瘤胃微生物脲酶抑制剂的研究有限。脲酶辅助蛋白 UreG 在促进脲酶成熟中起着关键作用，是设计脲酶抑制剂的新靶标。本研究的目的是通过靶向 UreG 从黄连中的主要原小檗碱类化合物中选择潜在有效的瘤胃微生物脲酶抑制剂。我们的研究结果表明，基于 UreG 的 GTPase 活性研究，盐酸小檗碱和表小檗碱比其他生物碱具有更高的抑制潜力。盐酸小檗碱对 UreG 的抑制为混合性，而表小檗碱的抑制动力学类型为非竞争性。此外，表小檗碱在抑制镍与 UreG 的结合以及诱导 UreG 二级结构变化方面比盐酸小檗碱更有效。分子建模为表小檗碱具有更高的抑制潜力提供了合理的结构基础，UreG 的 G1 基元和 G3 基元中的氨基酸残基与盐酸小檗碱的 D 环形成相互作用，而与表小檗碱的 A 环和 D 环相互作用。我们进一步证明了表小檗碱在瘤胃微生物发酵中的功效，可降低氨的释放和尿素的降解。总之，本研究清楚地表明，表小檗碱是一种有前途的候选物，可作为安全有效的瘤胃微生物脲酶抑制剂，并为未来调节反刍动物氮排泄提供了最佳策略和合适的饲料添加剂。关键点： • 表小檗碱是黄连中最有效的瘤胃脲酶抑制剂。 • 脲酶辅助蛋白 UreG 是设计脲酶抑制剂的有效靶标。 • 表小檗碱可作为天然饲料添加剂，减少反刍动物中 NH 的释放。
