Alternative substrates selective for S-adenosylmethionine synthetases from pathogenic bacteria
摘要:
S-adenosyl-L-methionine (AdoMet) synthetase catalyzes the production of AdoMet, the major biological methyl donor and source of methylene, amino, ribosyl, and aminopropyl groups in the metabolism of all known organism. In addition to these essential functions, AdoMet can also serve as the precursor for two different families of quorum sensing molecules that trigger virulence in Gram-negative human pathogenic bacteria. The enzyme responsible for AdoMet biosynthesis has been cloned, expressed and purified from several of these infectious bacteria. AdoMet synthetase (MAT) from Neisseria meningitidis shows similar kinetic parameters to the previously characterized Escherichia coli enzyme, while the Pseudomonas aeruginosa enzyme has a decreased catalytic efficiency for its MgATP substrate. In contrast, the more distantly related MAT from Campylobacter jejuni has an altered quaternary structure and possesses a higher catalytic turnover than the more closely related family members. Methionine analogs have been examined to delineate the substrate specificity of these enzyme forms, and several alternative substrates have been identified with the potential to block quorum sensing while still serving as precursors for essential methyl donation and radical generation reactions. (C) 2013 Elsevier Inc. All rights reserved.
Stable-Isotope Dimethylation Labeling Combined with LC−ESI MS for Quantification of Amine-Containing Metabolites in Biological Samples
作者:Kevin Guo、Chengjie Ji、Liang Li
DOI:10.1021/ac0704356
日期:2007.11.1
was found that deuterium labeling causes an isotopeeffect on the elution of labeled amines on RPLC but has no effect on HILIC LC. However, 13C-dimethylation does not show any isotopeeffect on either RPLC or HILIC LC, indicating that 13C-labeling is a preferred approach for relative quantification of amine-containing metabolites in different samples. The isotopicallylabeled 35 amine-containing analogues
and to develop mass spectrometry methods for the identification of all possible methylated amino acids for future metabolomic studies. In this study, all N‐methyl and N,N‐dimethyl amino acids were synthesized by the methylation of α‐amino acids and characterized by a GC‐MS method. The methylated amino acids were derivatized with ethyl chloroformate and analyzed by GC‐MS under EI and methane/CI conditions
甲基化是生物系统中必不可少的代谢过程,对于活生物体中的几种生物反应而言都非常重要。已知甲基化化合物参与大多数身体功能,其中一些充当生物标记。从理论上讲,所有α-氨基酸都可以被甲基化,并且在大多数动植物样品中都可能遇到。但是分析数据,尤其是质谱数据,仅可用于少数甲基化氨基酸。因此,至关重要的是产生质谱数据并开发质谱方法以鉴定所有可能的甲基化氨基酸,以用于未来的代谢组学研究。在这项研究中,所有N-甲基和N,N二甲基氨基酸是通过α-氨基酸的甲基化合成的,并通过GC-MS方法进行了表征。甲基化的氨基酸用氯甲酸乙酯衍生化,并在EI和甲烷/ CI条件下通过GC-MS分析。N-甲基(1-18)和N,N-二甲基氨基酸(19-35)的氯甲酸乙酯衍生物的EI质谱显示出丰富的[M-COOC 2 H 5 ] +离子。由于[M-COOC 2 H]中的C 2 H 4,CO 2((CO 2 + C 2 H 4))的损失而产生的碎片离子5
Synthesis of New Chiral Phase-transfer Catalysts and Their Application to Michael Additions
作者:Stefano Banfi、Mauro Cinquini、Stefano Colonna
DOI:10.1246/bcsj.54.1841
日期:1981.6
A series of chiral onium salts derived from (L)-(+)-methionine have been examined for the catalysis of Michael additions in phase-transfer conditions. The chemical yields are high, but no asymmetric induction was observed. Catalyst 6 represents the first example of an onium salt anchored to a polimeric matrix having a higher catalytic efficiency than its soluble counterpart.
N-alkylation of unprotected aminoacids. The catalytic system gives excellent selectivity toward monoalkylated α-amino acids and a high degree of retention of stereochemistry. A wide range of unprotected nonnatural aminoacids have been prepared. These compounds represent an array of building blocks that could be used for the direct synthesis of peptidomimetics. The synthesis of amino-acid-based surfactants