Mechanism of Phytochelatin Biosynthesis

当暴露于重金属如镉时，植物和真菌会合成称为植物螯合素的短肽。植物螯合肽是由三肽谷胱甘肽通过肽单位从一个谷胱甘肽分子转移到另一个而衍生的。编码合成植物螯合素的酶的基因，被称为植物螯合素合成酶，最近被克隆出来。研究计划的主要目标有三个方面：(i)定义植物螯合素合成酶的基本酶学。（ii）阐明表达植物螯合素合成酶不同形式的突变体的催化缺陷。（iii）植物螯合素合成酶的结晶和三维结构测定。这些研究将对转肽化反应产生新的见解，一般来说，特别是植物螯合素合成的机制。编码植物螯合素合成酶的基因也可用于改造植物以修复重金属污染。

Plants and fungi synthesize short peptides termed phytochelatins when exposed to heavy metals such as cadmium. Phytochelatins are derived from a tripeptide, glutathione, by the transfer of peptide units from one glutathione molecule to another. The gene encoding for the enzyme that synthesizes phytochelatins, named phytochelatin synthase, has recently been cloned. The main objectives of the research program are three-fold: (i) To define the basic enzymology of phytochelatin synthase. (ii) Elucidation of the catalytic defect in mutants expressing variant forms of phytochelatin synthase. (iii) Crystallization and three-dimensional structure determination of phytochelatin synthase. These studies will yield fresh insights into transpeptidation reactions, in general, and the mechanism of phytochelatin synthesis, in particular. The genes encoding phytochelatin synthase could also be used to engineer plants for the remediation of heavy metal pollution.