Biological Chemistry Laboratory, Department of Zoology, School of Life Sciences, North-Eastern Hill University, Shillong 793022, India.
Biosci Rep. 2021 Oct 29;41(10). doi: 10.1042/BSR20211634.
Glucosinolates, synthesized by the glucosinolate biosynthesis pathway, are the secondary metabolites used as a defence mechanism in the Brassicaceae plants, including Arabidopsis thaliana. The first committed step in the pathway, catalysed by methylthioalkylmalate (MAM) synthase (EC: 2.3.3.17), is to produce different variants of glucosinolates. Phylogenetic analyses suggest that possibly MAM synthases have been evolved from isopropylmalate synthase (IPMS) by the substitutions of five amino acid residues (L143I, H167L, S216G, N250G and P252G) in the active site of IPMS due to point mutations. Considering the importance of MAM synthase in Brassicaceae plants, Petersen et al. (2019) made an effort to characterise the MAM synthase (15 MAM1 variants) in vitro by single substitution or double substitutions. In their study, the authors have expressed the variants in Escherichia coli and analysed the amino acids in the cultures of E. coli in vivo. Since modifying the MAM synthases by transgenic approaches could increase the resistance of Brassicaceae plants for enhancing the defence effect of glucosinolates and their degraded products; hence, MAM synthases should be characterized in detail in vivo in A. thaliana along with the structural analysis of the enzyme for meaningful impact and for its imminent use in vivo.
硫代葡萄糖苷，由硫代葡萄糖苷生物合成途径合成，是拟南芥等十字花科植物作为防御机制使用的次生代谢物。该途径的第一步由甲基硫代丙二酸（MAM）合酶（EC：2.3.3.17）催化，产生不同变体的硫代葡萄糖苷。系统发育分析表明，MAM 合酶可能是由异丙基丙二酸合酶（IPMS）进化而来的，由于点突变，IPMS 的活性位点中取代了五个氨基酸残基（L143I、H167L、S216G、N250G 和 P252G）。考虑到 MAM 合酶在十字花科植物中的重要性，Petersen 等人（2019 年）努力通过单取代或双取代在体外对 MAM 合酶（15 个 MAM1 变体）进行了表征。在他们的研究中，作者在大肠杆菌中表达了这些变体，并分析了大肠杆菌培养物中的氨基酸。由于通过转基因方法修饰 MAM 合酶可以提高十字花科植物的抗性，从而增强硫代葡萄糖苷及其降解产物的防御效果；因此，应该在体内详细研究拟南芥中的 MAM 合酶，并对该酶进行结构分析，以便产生有意义的影响并为其在体内的即将应用做好准备。
