Insights into the Mechanism of the Cyanobactin Heterocyclase Enzyme
Insights into the Mechanism of the Cyanobactin Heterocyclase Enzyme
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DOI：
10.1021/acs.biochem.9b00084
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发表时间：
2019-04-23
期刊：
影响因子：
2.9
通讯作者：
Naismith, James H.
中科院分区：
文献类型：
--
作者：
Ge, Ying;Czekster, Clarissa Melo;Naismith, James H.
蓝藻杆菌素杂环酶与来自其他核糖体肽（RiPP）生物合成途径的杂环酶/环己基转移酶共享相同的催化结构域（YcaO）。这些酶在同一底物中处理多个残基（Cys/Thr/Ser）。半胱氨酸残基的加工以已知的顺序进行。我们表明苏氨酸的反应顺序是不同的，部分取决于底物内的前导肽。与其他YcaO结构域相反，据报道，其专门将ATP分解为ADP和无机磷酸盐，已经观察到氰基菌素杂环酶在催化过程中产生AMP和无机焦磷酸盐。我们剖析了与杂环化相关的核苷酸谱，并提出了一个统一的机制，其中ATP的γ-磷酸盐在激酶机制中转移到底物，以产生所有YcaO结构域共同的磷酸化中间体。在氰氧化菌素杂环酶中，这种磷酸化的中间体，在一定比例的周转中，与ADP反应产生AMP和焦磷酸。
Cyanobactin heterocyclases share the same catalytic domain (YcaO) as heterocyclases/cyclodehydratases from other ribosomal peptide (RiPPs) biosynthetic pathways. These enzymes process multiple residues (Cys/Thr/Ser) within the same substrate. The processing of cysteine residues proceeds with a known order. We show the order of reaction for threonines is different and depends in part on a leader peptide within the substrate. In contrast to other YcaO domains, which have been reported to exclusively break down ATP into ADP and inorganic phosphate, cyanobactin heterocyclases have been observed to produce AMP and inorganic pyrophosphate during catalysis. We dissect the nucleotide profiles associated with heterocyclization and propose a unifying mechanism, where the gamma-phosphate of ATP is transferred in a kinase mechanism to the substrate to yield a phosphorylated intermediate common to all YcaO domains. In cyanobactin heterocyclases, this phosphorylated intermediate, in a proportion of turnovers, reacts with ADP to yield AMP and pyrophosphate.