Peptide Epimerase Responsible for d-Amino Acid Introduction in Poly-γ-glutamic Acid Biosynthesis,Biomacromolecules

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Peptide Epimerase Responsible for d-Amino Acid Introduction in Poly-γ-glutamic Acid Biosynthesis
Biomacromolecules ( IF 5.5 ) Pub Date : 2023-12-14 , DOI: 10.1021/acs.biomac.3c01000
Hinata Kato ₁ , Moeka Sakuta ₁ , Takeshi Tsunoda ₂ , Yu Nakashima ₃ , Hiroyuki Morita ₃ , Yasushi Ogasawara ₂ , Tohru Dairi ₂

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Poly-γ-glutamic acid (PGA) is a natural polymer of d- and/or l-glutamic acid (Glu) linked by isopeptide bonds. We recently showed that PGA synthetase, an enzyme complex composed of PgsB, PgsC, and PgsA, uses only l-Glu for polymerization, and d-Glu residues are introduced by peptide epimerization. However, it remains unclear which of the three enzymes is responsible for epimerization because in vitro functional characterization of the membrane-associated PgsBCA complex has never been successful. Here, we performed gene exchange experiments and showed that PgsA is responsible for the epimerization. Additionally, we identified a region in PgsA that modulates epimerization activity based on homology modeling from the recently solved structure of MslH, which showed 53% identity to PgsA. Our results suggested that d/l-ratios of the PGA product can be altered by introducing amino acid substitutions in this region, which will be useful for the production of PGA with controlled d/l-ratios.

中文翻译：

肽差向异构酶负责聚-γ-谷氨酸生物合成中 d-氨基酸的引入

聚-γ-谷氨酸（PGA）是通过异肽键连接的d-和/或l-谷氨酸（Glu）的天然聚合物。我们最近表明，PGA 合成酶是一种由 PgsB、PgsC 和 PgsA 组成的酶复合物，仅使用l -Glu 进行聚合，并通过肽差向异构化引入d -Glu 残基。然而，目前尚不清楚这三种酶中哪一种负责差向异构化，因为膜相关 PgsBCA 复合物的体外功能表征从未成功。在这里，我们进行了基因交换实验，结果表明 PgsA 负责差向异构化。此外，我们根据最近解析的 MslH 结构的同源模型，确定了 PgsA 中调节差向异构化活性的区域，该区域与 PgsA 有 53% 的同一性。我们的结果表明，可以通过在该区域引入氨基酸取代来改变 PGA 产品的d / l比，这将有助于生产具有受控d / l比的 PGA。

更新日期：2023-12-14

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