A papain-like enzyme at work: native and acyl-enzyme intermediate structures in phytochelatin synthesis.
A papain-like enzyme at work: native and acyl-enzyme intermediate structures in phytochelatin synthesis.
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DOI：
10.1073/pnas.0505833102
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发表时间：
2005-12
影响因子：
11.1
通讯作者：
D. Vivarès;P. Arnoux;D. Pignol
中科院分区：
文献类型：
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作者：
D. Vivarès;P. Arnoux;D. Pignol
植物螯合素合成酶（PCS）是植物体内重金属解毒的关键酶。PCS催化谷胱甘肽（GSH）衍生肽（称为植物螯合素或PC）的产生，这些肽在液泡隔离之前结合重金属离子。该酶还可以水解GSH和GS缀合的异生物质。在蓝细菌念珠藻中，该酶（NsPCS）仅包含真核生物合酶的催化结构域，并且可以作为GSH水解酶和弱的肽连接酶。在2.0-A分辨率下解析的天然形式的NsPCS的晶体结构显示NsPCS是属于半胱氨酸蛋白酶的木瓜蛋白酶超家族的二聚体，具有保守的催化机制。此外，在1.4-A分辨率下作为与GSH的复合物解析的蛋白质的结构揭示了γ-谷氨酰半胱氨酸酰基-酶中间体稳定在邻近第二推定GSH结合位点的蛋白质的空腔中。GSH水解酶和PCS活性的酶进行了讨论，在这两种结构的光。
Phytochelatin synthase (PCS) is a key enzyme for heavy-metal detoxification in plants. PCS catalyzes the production of glutathione (GSH)-derived peptides (called phytochelatins or PCs) that bind heavy-metal ions before vacuolar sequestration. The enzyme can also hydrolyze GSH and GS-conjugated xenobiotics. In the cyanobacterium Nostoc, the enzyme (NsPCS) contains only the catalytic domain of the eukaryotic synthase and can act as a GSH hydrolase and weakly as a peptide ligase. The crystal structure of NsPCS in its native form solved at a 2.0-A resolution shows that NsPCS is a dimer that belongs to the papain superfamily of cysteine proteases, with a conserved catalytic machinery. Moreover, the structure of the protein solved as a complex with GSH at a 1.4-A resolution reveals a gamma-glutamyl cysteine acyl-enzyme intermediate stabilized in a cavity of the protein adjacent to a second putative GSH binding site. GSH hydrolase and PCS activities of the enzyme are discussed in the light of both structures.