据报道,用于合成S-腺苷-L-甲硫氨酸 (SAM) 类似物的化学酶平台与下游 SAM 利用酶兼容。合成了 44 种非天然 S/Se 烷基化 Met 类似物,并将其用于探测五种不同的蛋氨酸腺苷转移酶 (MAT) 的底物特异性。人类 MAT II 是所分析的 MAT 中最受允许的之一,并且能够化学酶合成 29 种非天然 SAM 类似物。作为天然产物“烷基随机化”可行性的概念证明,通过使用耦合的 hMAT2-RebM 系统(RebM 是参与瑞贝卡霉素的糖 C4'- O-甲基转移酶)生成了一小组差异烷基化吲哚并咔唑类似物。生物合成)。在单个容器中耦合 SAM 合成和利用的能力避免了与 SAM 类似物快速分解相关的问题,从而为进一步研究各种 SAM 利用酶打开了大门。
The methyltransferase NovO cloned from Streptomyces spheroides could be heterologously produced as soluble and active enzyme in Escherichia coli. Sequencing of the cloned novO gene revealed differences to the GenBank entry AAF67508.1 resulting in a different amino acid at position 223 (Cys instead of Ser). A generated variant containing a Ser residue at this position, however, resulted in poor ability to express soluble and enzymatically active protein. Characterization of NovO revealed a type I methyltransferase that performs its action as a dimer in solution. Functional elements include the conserved S-adenosyl-L-methionine (SAM) binding site (consensus: E/DXXXGXG) as DLCCGSG (residues 45-51). Mutation analyses of the respective amino acids verified their importance for cofactor binding and enzyme activity. In soluble protein fractions of mutants D45N and G49A the calculated kat values decreased from 2.5 x 10(-2) s(-1) of the wild-type protein to 9.7 x 10(-4) s(-1) and 1.2 x 10(-3) s(-1), respectively. A histidine at position 15 was identified as the catalytic base in the methyl transfer reaction. The analysis of purified enzyme preparations showed that the transfer of allyl groups via the SAM analog allyl-SAH occurs with a fourfold increased K-cat of 11 x 10(-3) s(-1) compared to 3.2 x 10(-3) s(-1) for methyl transfer. However, the evolutionary design toward SAM is obvious from the Km value of 0.06 mM compared to 0.22 mM for allyl-SAH. (C) 2012 Elsevier B.V. All rights reserved.