Novel Epimerase Activity in Syringomycin Biosynthesis

描述（由申请人提供）： 由非核糖体肽合成酶（NRPS）产生的肽在治疗上用作抗生素、抗肿瘤剂和免疫抑制剂。这种活动提高了对负责其合成的模块化酶部分的研究兴趣，其长期目标是互换模块以影响新治疗剂文库的组合生物合成。该建议的重点是确定的起源差向异构酶活性的NRPS从假单胞菌产生的植物毒素黄曲霉素。具体地，瑞幸霉素含有多个D-氨基酸残基，但瑞幸霉素NRPS，像假单胞菌属来源的所有其他NRPS一样，不含有通常在革兰氏阳性细菌的NPRS装配线中发现的50 kD差向异构酶结构域。我们建议确定存在的其他三个结构域（腺苷酸化，硫酯化和缩合）中的哪一个包含新的双重活性，从而作为有效的差向异构化结构域，作为收集插入和延长D-与L-氨基酸残基的结构域的前奏。

DESCRIPTION (provided by applicant): Peptides produced by nonribosomal peptide synthetases (NRPSs) function therapeutically as antibiotics, antitumor agents, and immuno-suppressants. This activity has heightened interest in studying the modular enzyme parts responsible for their synthesis, with the long-term goal of interchanging modules to affect the combinatorial biosynthesis of libraries of new therapeutic agents. This proposal is focused on determining the origin of the epimerase activity in the NRPS from Pseudomas syringae that produces the phytotoxin syringomycin. Specifically, syringomycin contains multiple D-amino acid residues, but the syringomycin NRPS, like all other NRPSs of Pseudomonas origin, does not contain the 50 kD epimerase domains typically found in the NPRS assembly lines of gram positive bacteria. We propose to determine which one of the other three domains that are present (adenylation, thioesterification, and condensation) contains novel dual activity, thereby functioning as an effective epimerization domain, as a prelude to collecting domains that insert and elongate D- vs L-amino acid residues.