Biomedical Sciences Research Complex , University of St Andrews , St Andrews, Fife KY16 9ST , United Kingdom.
Research Complex at Harwell , Didcot, Oxon OX11 0FA , United Kingdom.
Biochemistry. 2019 Apr 23;58(16):2125-2132. doi: 10.1021/acs.biochem.9b00084. Epub 2019 Apr 5.
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 γ-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.
蓝细菌环肽异构酶与其他核糖体肽（RiPPs）生物合成途径的异构酶/环脱水酶具有相同的催化结构域（YcaO）。这些酶在同一底物中处理多个残基（半胱氨酸/苏氨酸/丝氨酸）。半胱氨酸残基的加工过程具有已知的顺序。我们展示了苏氨酸的反应顺序不同，部分取决于底物中的前导肽。与其他已报道的仅将 ATP 分解为 ADP 和无机磷酸盐的 YcaO 结构域不同，蓝细菌环肽异构酶在催化过程中已观察到产生 AMP 和焦磷酸。我们剖析了与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-磷酸通过激酶机制转移到底物上，生成所有 YcaO 结构域共有的磷酸化中间产物。在蓝细菌环肽异构酶中，该磷酸化中间产物在部分转化中与 ADP 反应生成 AMP 和焦磷酸。
