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| Advances in study on phytochelatin synthase in plants |
| MEI Lei1,2, ZHU Ye1, XIAO Qinzhi3, CHEN Jinhong1, ZHU Shuijin1* |
(1. Institute of Crop Sciences, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou 310058, China; 2. Department of Plant Sciences, University of Cambridge, Cambridge CB23EA, United Kingdom; 3. Shaoyang Tobacco Monopoly Bureau, Shaoyang 422000, Hunan, China)
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Abstract Phytochelatin (PC), which is produced under catalyzation of phytochelatin synthase (PCS), plays a key role in phytoremediation as its ability of conjugating heavy metal ion in plants. Intensive research on phytochelatin synthase is of great significance to understand the mechanism of heavy metal resistance in plants, as well as inspires on strategies for creating engineering plants to ameliorate soil contaminated by heavy metal. This review was based on five aspects including bifunctional enzyme property, gene expression and enzymology feature, species distribution and phylogeny, catalytic active center, and activating mode. PCS mainly catalyzes the process of phytochelatin synthesis, as well as acts as peptidase. The gene expression of PCS is constitutive, whereas it can be regulated by heavy metal ion like Cd2+ in a few species, and PCS is activated by some metal ions in which Cd2+ is the most effective. It is widely distributed and can be found in organism kingdom such as yeast and nematode besides plants where PCS family members have closer genetic relationship than in other species, which infer its roles in plant’s adaption to environment. The catalytic center of PCS is located at N-terminal, and the three amino acid residues corresponding to Cys70, His183 and Asp201 in cyanobacterium absolutely conserved in all species. The heavy metal activation of PCS is believed to be related to cysteine, including two hypotheses of direct contact activation of heavy metals and formation of indirect intermediates. At the last part of this review, further discussions and prospects are given on multiple functions, gene expression, activating mechanism of PCS, as well as application regarding to the genes, aiming to provide some insights and references for further study.
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Published: 30 October 2018
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植物络合素合酶及其基因研究进展
植物络合素（phytochelatin, PC）能与重金属产生络合反应，在植物解除重金属毒害过程中起关键作用，其在生物体内的合成受植物络合素合酶（phytochelatin synthase, PCS）控制。深入研究植物络合素合酶对理解植物对抗重金属胁迫的机制，以及运用基因工程手段创造工程植物来修复重金属污染环境具有重要意义。本文从PCS的双功能酶特性、基因表达和酶学特征、物种分布和亲缘关系、催化活性中心及激活模式5 个方面作简要评述。PCS的主要功能为催化合成植物络合素，同时具有肽酶的副功能；PCS基因的表达是组成型的，在少数物种中，其表达也受Cd2+等重金属离子诱导，而酶的活性受部分金属离子调控，其中以Cd2+效果最为明显。PCS分布广泛，不是植物所独有的，在酵母、线虫等物种中同时存在，然而该酶在植物中同源性较高，在其他物种中较低，暗示其在植物对环境适应过程中具有某些重要作用。PCS的催化中心位于N-基端，其中与藻青菌中Cys70、His183 和Asp201 相对应的3 个氨基在所有物种中为严格保守；PCS的重金属活化被认为与其含半胱氨酸有关，包含重金属直接接触活化和形成间接中间物活化2 种假说。最后对PCS的多功能性、基因表达特性、酶激活机制及此基因的利用进行了展望，旨在为与PCS相关的研究提供参考。
关键词：
植物络合素合酶,
双功能酶,
亲缘关系,
基因表达特征,
活化机制
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