Significance
Many enzymes perform desirable biochemical transformations, but are not suitable to use as biocatalysts outside of the cell. In particular, enzymes from heteromeric complexes typically have decreased activity when removed from their protein partners. We used directed evolution to restore the catalytic efficiency of the tryptophan synthase β-subunit (TrpB), which synthesizes
l
-tryptophan from
l
-serine and indole, surpassing the activity of the native complex. Experiments show that activating mutations promote catalysis through the same mechanism as partner protein binding, establishing that isolated subunits may be readily reactivated through directed evolution. Engineering TrpB for stand-alone function restored high activity with indole analogs, providing a simplified enzyme platform for the biocatalytic production of noncanonical amino acids.
标题:重要性
许多酶执行令人满意的生化转化,但通常不适合在细胞外作为生物催化剂使用。特别是,异源复合物中的酶通常在与其蛋白质伙伴分离后活性降低。我们利用定向进化恢复色氨酸合成酶β亚基(TrpB)的催化效率,该亚基从丝氨酸和吲哚合成l-色氨酸,超越了天然复合物的活性。实验证明,激活突变通过与伙伴蛋白结合相同的机制促进催化,表明隔离的亚基可以通过定向进化轻松重新激活。将TrpB工程化为独立功能可恢复与吲哚类似物的高活性,为非规范氨基酸的生物催化生产提供了简化的酶平台。