Investigation of AMA Synthase from <i>Pyrenophora teres</i> f. <i>teres</i> 0‐1 for the Synthesis of Aspergillomarasmine A Analogues and Non‐canonical Amino Acids

The fungal natural product aspergillomarasmine A (AMA) is an inhibitor of metallo‐β‐lactamases and a promising co‐drug candidate for reversing bacterial β‐lactam resistance. The biosynthesis of AMA from L‐Asp and O‐phospho‐L‐serine is catalyzed by AMA synthase, which possesses high synthetic potential for the biocatalytic preparation of AMA and related aminopolycarboxylic acids. Here, we identified and structurally characterized an AMA synthase from Pyrenophora teres f. teres 0‐1 (PteAMAS). Crystallographic analysis revealed a unique homotetrameric fold and a highly hydrophilic active site, which supports the PLP‐dependent β‐replacement catalytic mechanism. Furthermore, we demonstrated the utility of PteAMAS for the biocatalytic synthesis of AMA and its analogues, achieving structural diversification of the APA1 moiety through a modular two‐enzyme system involving PteAMAS and a selective C‐N lyase, namely EDDS lyase or 3‐methylaspartate ammonia lyase variant MAL‐Q73A. In addition, we exhibited the usefulness of PteAMAS for convenient synthesis of various S‐alkyl, ‐aryl, and ‐arylalkyl substituted L‐cysteines, which are valuable non‐canonical amino acids with broad pharmaceutical applications. The present study has not only provided the structural basis for catalysis and substrate recognition by PteAMAS, but also paved the way for biocatalytic preparation of structurally complex AMA analogues and various non‐canonical amino acids.