The Seed-Specific Rutin-Degrading Enzyme FtBGLU29 is a Key Factor Promoting the Accumulation of the Bitter Compound Quercetin in Tartary Buckwheat

Rutin-degrading enzymes play a crucial role in catalyzing the hydrolysis of rutin (quercetin 3-O-rutinoside) into the bitter compound quercetin, contributing significantly to the bitterness of Tartary buckwheat (Fagopyrum tataricum) (TB). Mitigating this bitterness is vital for improving the palatability and marketability of TB products. In this study, we integrated genomic and transcriptomic data with molecular docking analyses to identify 12 potential rutin-degrading enzymes in TB. Among them, FtBGLU29 exhibited a stable binding affinity for rutin and significantly higher expression levels, specifically in TB seeds. This unique expression was confirmed through Native-PAGE and MALDI-TOF/TOF-MS, which identified FtBGLU29 as the predominant rutin-degrading enzyme in TB seeds. In vitro hydrolysis experiments revealed that FtBGLU29 efficiently catalyzes the conversion of rutin to quercetin upon the hydration of TB flour. Functional studies showed that FtBGLU29 overexpression in TB seeds significantly enhanced the rutin hydrolysis rate relative to the control group (p < 0.05). In conclusion, this study establishes FtBGLU29 as a key enzyme in the degradation of rutin in TB seeds, highlighting its critical role in enhancing the enzymatic conversion efficiency and potentially reducing the bitterness of TB products.