Methylation Reactions Research Articles

Abundant Lewis acidic sites of peculiar fibrous silica zeolite X enhanced toluene conversion in side chain toluene methylation

Side chain toluene methylation reaction (SCTM) is a reliable reaction to produce styrene and ethylbenzene from toluene. Nevertheless, due to the lack of efficient catalyst caused by less Lewis acid sites and mesoporosity properties, the challenges in this SCTM reaction are still ongoing. Hence, this work is accomplished to gain a better understanding in designing a robust catalyst for side chain toluene methylation. Herein, this work emphasizes the uniqueness of top-notch metal-free fibrous silica zeolite X (FZX) by microemulsion method. This FZX showed superior catalytic activity towards side chain methylation with 15.9% yield of styrene and ethylbenzene, which was 16-fold higher compared to the commercial zeolite X (CZX) catalyst. This was achieved by the excellent properties of dendrimeric silica fibers of FZX possessing high concentration of basic sites and Lewis acid sites as well as high mesoporosity, as proved by the FTIR-Pyrrole, FTR-Pyridine and nitrogen physisorption analyses respectively. The presence of intermediates was confirmed by in-situ FTIR toluene-methanol. 27Al MAS NMR analysis proved that the presence of excessive extraframework alumina (EFAl) species could act as additional Lewis acid sites in FZX to enhance toluene adsorption on the FZX catalyst, thus improving the toluene conversion and desired styrene and ethylbenzene products. Silica MCM41 exhibited lower yield of styrene and ethylbenzene by the fact imbalance of acid base property of catalyst. The kinetic study proved that the side chain toluene methylation occurred via dissimilar dual site mechanism of Langmuir-Hinshelwood. This rationally designed metal-free FZX demonstrates its high potential in polymer and/or petrochemical as well as other industrial applications.

Phospholipid N-Methyltransferases Produce Various Methylated Phosphatidylethanolamine Derivatives in Thermophilic Bacteria.

One of the most common pathways for the biosynthesis of the phospholipid phosphatidylcholine (PC) in bacteria is the successive 3-fold N-methylation of phosphatidylethanolamine (PE) catalyzed by phospholipid N-methyltransferases (Pmts). Pmts with different activities have been described in a number of mesophilic bacteria. In the present study, we identified and characterized the substrate and product spectra of four Pmts from thermophilic bacteria. Three of these enzymes were purified in an active form. The Pmts from Melghirimyces thermohalophilus, Thermostaphylospora chromogena, and Thermobifida fusca produce monomethyl-PE (MMPE) and dimethyl-PE (DMPE). T. fusca encodes two Pmt candidates, one of which is inactivated by mutation and the other is responsible for the accumulation of large amounts of MMPE. The Pmt enzyme from Rubellimicrobium thermophilum catalyzes all three methylation reactions to synthesize PC. Moreover, we show that PE, previously reported to be absent in R. thermophilum, is in fact produced and serves as a precursor for the methylation pathway. In an alternative route, the strain is able to produce PC by the PC synthase pathway when choline is available. The activity of all purified thermophilic Pmt enzymes was stimulated by anionic lipids, suggesting membrane recruitment of these cytoplasmic proteins via electrostatic interactions. Our study provides novel insights into the functional characteristics of phospholipid N-methyltransferases in a previously unexplored set of thermophilic environmental bacteria. IMPORTANCE In recent years, the presence of phosphatidylcholine (PC) in bacterial membranes has gained increasing attention, partly due to its critical role in the interaction with eukaryotic hosts. PC biosynthesis via a three-step methylation of phosphatidylethanolamine, catalyzed by phospholipid N-methyltransferases (Pmts), has been described in a range of mesophilic bacteria. Here, we expand our knowledge on bacterial PC formation by the identification, purification, and characterization of Pmts from phylogenetically diverse thermophilic bacteria and thereby provide insights into the functional characteristics of Pmt enzymes in thermophilic actinomycetes and proteobacteria.

Conversion of syngas to triptane-rich liquid hydrocarbons via oxygenates

The triptane-rich liquid hydrocarbons are produced from syngas via oxygenates in two stages: in the first stage the oxygenates (methanol and dimethyl ether) are formed from CO + H2 over the Cu-Zn-Al-catalyst; in the second stage the oxygenates are converted to triptane-rich liquid hydrocarbons over the combined Mg-HZSM-5/Pd-La-HY catalyst. Over the Mg-HZSM-5, light olefins are formed in high yield, while the formation of triptane occurs over the Pd-La-HY, which is active in the isomerization of aliphatic hydrocarbons and in the alkylation of light iso-paraffins with light olefins. The increased water content in the reaction zone was found to lead to an increase in the yield of gaseous products. Water acts as an inhibitor of chain growth and methylation reactions and leads to the accumulation of methanol in the condensate. For efficient and stable (more than 72 h) operation of Mg-HZSM-5/Pd-La-HY, the concentration of water in the feedstock should not exceed 10 wt. %.

Ru-Catalyzed Selective Catalytic Methylation and Methylenation Reaction Employing Methanol as the C1 Source.

Methanol can be employed as a green and sustainable methylating agent to form C-C and C-N bonds via borrowing hydrogen (BH) methodology. Herein we explored the activity of the acridine-derived SNS-Ru pincer for the activation of methanol to apply it as a C1 building block in different reactions. Our catalytic system shows great success toward the β-C(sp3)-methylation reaction of 2-phenylethanols to provide good to excellent yields of the methylated products. We investigated the mechanistic details, kinetic progress, and temperature-dependent product distribution, which revealed the slow and steady generation of in situ formed aldehyde, is the key factor to get the higher yield of the β-methylated product. To establish the environmental benefit of this reaction, green chemistry metrics are calculated. Furthermore, dimerization of 2-naphthol via methylene linkage and formation of N-methylation of amine are also described in this study, which offers a wide range of substrate scope with a good to excellent yield.

Metabolites Identification of Chemical Constituents From the Eggplant (Solanum melongena L.) Calyx in Rats by UPLC/ESI/qTOF-MS Analysis and Their Cytotoxic Activities.

Eggplant (Solanum melongena L.) Calyx is a medicinal and edible traditional Chinese medicine with anti-inflammatory, anti-oxidant, and anti-cancer properties. However, the pharmacodynamic components and metabolic characteristics remain unclear. Amide and phenylpropanoid were the two main constituents, and four amides, including n-trans-p-coumaroyltyramine (1), n-trans-p-coumaroyloctopamine (2), n-trans-p-coumaroylnoradrenline (3), n-trans-feruloyloctopamine (4), and a phenylpropanoid neochlorogenic acid (5) were selected. In this study, these five representative compounds showed cytotoxic activities on A549, HCT116, and MCF7 cells. In addition, the metabolites of 1–5 from the eggplant calyx in rats were identified. In total, 23, 37, 29, and 17 metabolites were separately characterized in rat plasma, urine, feces, and livers, by UPLC/ESI/qTOF-MS analysis. The metabolism of amides and phenylpropanoid was mainly involved in hydroxylation, methylation, glucuronidation, or sulfation reactions. Two hydroxylated metabolites (1-M2 and 2-M3) were clearly identified by comparison with reference standards. Rat liver microsome incubation experiments indicated that P450 enzymes could hydroxylate 1–5, and the methylation reaction of the 7-hydroxyl was also observed. This is the first study on the in vivo metabolism of these compounds, which lays a foundation for follow-up studies on pharmacodynamic evaluations and mechanisms.

Regio‐ and Diastereo‐Selective Biomimetic Synthesis of (±)‐ϵ‐Viniferin by NIS and Resveratrol

AbstractIn this work, we describe the synthesis of (±)‐permethylated‐ϵ‐viniferin from resveratrol by successive iodination, methylation and dehalogenation reactions. Iodination reaction by N‐iodosuccinimide (NIS) was studied to optimize and confirm a proposed radical mechanism. Switching to acetyl protecting group, a new straightforward regio‐ and diastereo‐selective biomimetic synthesis of (±)‐ϵ‐viniferin was obtained. Permethylated and free ϵ‐viniferin were isolated up to 20 %yield.

Comparative Study of Synthesis, Structural and Antioxidant Activity In Vitro of Some New Carboxylic α,α-diaminodiesters Derivatives

Considering the richness of heterocyclic chemistry, and the diversity of applications it possesses, in the present work we were interested in preparing new polyfunctional α,α-diaminodiesters derived from glycine, via the N-alkylation reaction of methyl 2-azido-2-benzamidoacetate with a series of heterocyclic and non-heterocyclic carboxylic aminoesters, using different bases. The structures of the synthesized molecules were characterized by 1D and 2D NMR spectroscopy, mass spectrometry (MS-ESI) and elemental analysis. Two compounds from this series were isolated as single crystals and their chemical structures were determined by X-ray diffraction. The antioxidant effect of the synthesized compounds was tested in vitro using the free radical scavenging power (DPPH) and reducing power (FRAP) tests. The results show that the different extracts tested have a relatively high antioxidant power compared to the positive control considered, especially for the compound methyl 2-benzamido-2-(2-methoxy-2-oxo-1-phenylethyl)amino)acetate, which showed a very strong antiradical power and reducing power.

Mutual Correlation between Non-Coding RNA and S-Adenosylmethionine in Human Cancer: Roles and Therapeutic Opportunities.

Simple SummaryNon-coding RNAs and S-adenosylmethionine, the methyl donor required in all epigenetic methylation reactions, have emerged in recent years as crucial players in the modulation of gene expression in different types of human cancers. This review summarizes the most recent findings on reciprocal regulation between AdoMet and non-coding RNAs. AdoMet was found to exert anticancer activity through epigenetic regulation of non-coding RNAs, including microRNAs, long non-coding RNAs and circular RNAs. On the other hand, several microRNAs and long non-coding RNAs have been reported to display regulatory effects on the expression of genes involved in AdoMet synthesis and metabolism. Increasing knowledge on the relationship between AdoMet and non-coding RNAs will provide insights for further development of diagnostic and therapeutic strategies for cancer treatments.Epigenetics includes modifications in DNA methylation, histone and chromatin structure, and expression of non-coding RNAs (ncRNAs), especially microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). Knowledge of the relationships between S-adenosylmethionine (AdoMet or SAM), the universal methyl donor for all epigenetic methylation reactions and miRNAs or lncRNAs in human cancer may provide helpful insights for the development of new end more effective anticancer therapeutic approaches. In recent literature, a complex network of mutual interconnections between AdoMet and miRNAs or lncRNAs has been reported and discussed. Indeed, ncRNAs expression may be regulated by epigenetic mechanisms such as DNA and RNA methylation and histone modifications. On the other hand, miRNAs or lncRNAs may influence the epigenetic apparatus by modulating the expression of its enzymatic components at the post-transcriptional level. Understanding epigenetic mechanisms, such as dysregulation of miRNAs/lncRNAs and DNA methylation, has become of central importance in modern research. This review summarizes the recent findings on the mechanisms by which AdoMet and miRNA/lncRNA exert their bioactivity, providing new insights to develop innovative and more efficient anticancer strategies based on the interactions between these epigenetic modulators.

Targeted Metabolomics: The LC-MS/MS Based Quantification of the Metabolites Involved in the Methylation Biochemical Pathways.

Biochemical methylation reactions mediate the transfer of the methyl group regulating vital biochemical reactions implicated in various diseases as well as the methylation of DNA regulating the replication processes occurring in living organisms. As a finite number of methyl carriers are involved in the methyl transfer, their quantification could aid towards the assessment of an organism’s methylation potential. An Hydrophilic Interaction Chromatography-Liquid Chromatography Multiple Reaction Monitoring (HILIC-LC-MRM) mass spectrometry (MS) methodology was developed and validated according to Food & Drug Administration (FDA), European Medicines Agency (EMA), and International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) for the simultaneous determination of nine metabolites i.e., B12, folic acid, 5-methyltetrahydrofolate, S-adenosylmethionine, S-adenosylhomocysteine, betaine, phosphocholine, N,N-dimethylglycine, and deoxythymidine monophosphate in human blood plasma. The sample pretreatment was based on a single step Solid-phase extraction (SPE) methodology using C18 cartridges. The methodology was found to accurately quantitate the analytes under investigation according to the corresponding dynamic range proposed in the literature for each analyte. The applicability of the method was assessed using blood donor samples and its applicability demonstrated by the assessment of their basal levels, which were shown to agree with the established basal levels. The methodology can be used for diagnostic purposes as well as for epigenetic screening.

Toxicity assessment of dimethyl carbonate following 28 days repeated inhalation exposure.

Dimethyl carbonate (DMC) has been used as a reagent in methylation reactions, can be used as paints, coatings, and adhesives, and is a chemical that is being used increasing, which poses a health hazard to workers who handle it. So, the toxic reactions of F344 rats with inhalation exposure to 600, 1600, and 5000 ppm concentrations for 6 hours, 5 days a week, 4 weeks was evaluated. During the exposure period, general signs were observed, body weight and food consumption were measured, and hematologic and blood biochemical tests, organ weight measurements, necropsy, and histopathological examination were performed after the end of exposure. During the exposure period, dimethyl carbonate was exposed to an average of 599.26±31.40, 1614.64±80.79 and 5106.83±297.13 ppm in the chambers of the T1, T2 and T3 test groups, respectively. During the test period, general signs, weight change, food consumption, organ weight measurement, necropsy, and histopathological examination did not show any effects related to exposure to the test substance. However, as a result of blood and blood biochemical tests, an increase in AST, ALP, APTT, and PT levels was observed. From these results, it is judged that liver is the target organ when repeated inhalation exposure of dimethyl carbonate, the test substance, for 4 weeks, and the exposure-related effects of the test substance were observed at PT and ALP levels up to 600 ppm exposure concentration, but NOEC (No Observed Effect Concentration) was determined to be less than 600 ppm because it was not judged as an adverse effect.

Theoretical insights into the enhancement of 1-Methyl-2,4,5-trinitroimidazole yield by exchanging of group introduction order

During the synthesis of 1-methyl-2,4,5-trinitroimidazole (MTNI), the product yield was affected by group introduction order. This phenomenon has not been explained in the reaction mechanism. In this paper, the DFT method was used to study the synthesis mechanism. For the nitration reaction, an N-H⋯O hydrogen bond was formed between the midazole ring and water molecule in the solution to promote the nitration reaction, so the nitration mechanism was affected by the introduction of methyl group at the N site. For the methylation reaction, the electrophilic attack of the methyl group was affected by the introduction of more electron-withdrawing nitro group.

STUDY ON SYNTHESIS AND STRUCTURE OF SOME HYDRAZONES FROM 3,4-DIMETHOXY-2-NITROBENZALDEHYDE

Three new hydrazones were synthesized by condensation reaction between 3,4-dimethoxy-2-nitrobenzaldehyde and aryl hydrazine hydrochlorides. 3,4-Dimethoxy-2-nitrobenzaldehyde needed for the Schiff base-imine condensation reaction was synthesized from vanillin through esterification, nitration, hydrolysis, and methylation reactions. All products were purified by re-crystallization in a suitable solvent. The structures of three new hydrazones were determined by 1H NMR, 13C NMR, and MS.

Synthesis of methyl 1,5‐diaryl‐1H‐pyrrole‐2‐carboxylates via acid‐catalyzed ring‐opening/ring‐closure sequence

AbstractA facile synthesis of methyl 1,5‐diaryl‐1H‐pyrrole‐2‐carboxylates was reported in this article. Acid‐catalyzed reaction of methyl 2‐aroyl‐1‐phenoxycyclopropanecarboxylates with aromatic amines underwent smoothly to give methyl 1,5‐diaryl‐1H‐pyrrole‐2‐carboxylates in high to excellent yields under mild conditions.

A density functional theory study of the hydride shift in the Eschweiler–Clarke reaction

AbstractThe Eschweiler–Clarke (the amine methylation) reaction was investigated by density functional theory (DFT) calculations. First, a reaction model of H3CNH2 + HC(O)OH + CH2O + (H2O)3 → (H3C)2NH + CO2 + (H2O)4 was employed for geometry optimizations. Geometries and activation free energies of transition states (TSs) by eight DFTs, B2PLYP‐D3, B3LYP, B3LYP‐D, BP86‐D, PBE0‐D, M06‐2X, wB97X‐D, and APF‐D, along with MP2 were compared. Four elementary processes were obtained. The rate‐determining step is of the hydride‐transfer TS, H3CN+HCH2 + HCO2− → H3CNHCH3 + CO2. Whereas BP86‐D and APF‐D gave underestimated energies, M06‐2X was found to be a reasonable DFT to trace the present reaction. Second, by the use of M06‐2X/6‐311++G**, hydride‐shift TSs were examined for various sizes of the water cluster (H2O)n, and the controversial two mechanisms were evaluated. It was suggested that the first formic acid contributes to formation of the iminium ion H3CN+HCH2 and the second formic acid works for the hydride transfer. The Eschweiler–Clarke reaction was described by the scheme, R1R2NH + H2CO + (HCOOH)2 + (H2O)n → R1R2NCH3 + CO2 + HCO2− + H3O+(H2O)n.

MRNA Expressions of Methylation Related Enzymes and Duration of Thermal Conditioning in Chicks.

DNA methylation regulates gene expression by modifying the nucleosome structure of DNA, without altering the gene sequence. It has been reported that DNA methylation reactions are catalyzed by several enzymes. In chickens, thermal conditioning treatment affects the central DNA methylation levels. The purpose of this study was to clarify the changes in DNA methylation and demethylation factors during thermal conditioning in the hypothalamus of 3-day-old chicks. Male chicks (3-days old) were exposed to 40±0.5°C as a thermal conditioning treatment for 1, 2, 6, 9, or 12 h. The control chicks were kept in a thermoneutral zone (30±0.2°C). After thermal conditioning, the mRNA levels of DNA methyltransferase (DNMT)-1, -3a, -3b, and ten-eleven translocation (TET)-1, -2, and -3 in the hypothalamus were measured by q-PCR. The mRNA levels of DNMT-3a and TET-1 were increased by thermal conditioning. Moreover, the expression level of TET-1 increased with the loading time of the thermal conditioning. The gene expressions of DNMT-1, DNMT-3b, TET-2, and TET-3 were not affected by thermal conditioning. Since DNMT-3a is a catalyst for de-novo DNA methylation and TET-1 catalyzes the oxidation of methylated cytosine, it is suggested that the thermal conditioning increased the activation of DNA methylation and demethylation factors, which occur in the hypothalamus of neonatal chicks.

The Resistance Responses of Potato Plants to Potato Virus Y Are Associated with an Increased Cellular Methionine Content and an Altered SAM:SAH Methylation Index.

Plant-virus interactions are frequently influenced by elevated temperature, which often increases susceptibility to a virus, a scenario described for potato cultivar Chicago infected with potato virus Y (PVY). In contrast, other potato cultivars such as Gala may have similar resistances to PVY at both normal (22 °C) and high (28 °C) temperatures. To elucidate the mechanisms of temperature-independent antivirus resistance in potato, we analysed responses of Gala plants to PVY at different temperatures using proteomic, transcriptional and metabolic approaches. Here we show that in Gala, PVY infection generally upregulates the accumulation of major enzymes associated with the methionine cycle (MTC) independently of temperature, but that temperature (22 °C or 28 °C) may finely regulate what classes accumulate. The different sets of MTC-related enzymes that are up-regulated at 22 °C or 28 °C likely account for the significantly increased accumulation of S-adenosyl methionine (SAM), a key component of MTC which acts as a universal methyl donor in methylation reactions. In contrast to this, we found that in cultivar Chicago, SAM levels were significantly reduced which correlated with the enhanced susceptibility to PVY at high temperature. Collectively, these data suggest that MTC and its major transmethylation function determines resistance or susceptibility to PVY.

Effect of Lewis/Brønsted acid sites in HZSM−5 zeolite on the selectivity of para-xylene during methylation of toluene with methanol

• The participation of Lewis acid site is good for the dissociation of methanol. • The activity of methanol dissociation has positive correlation with the acid strengths of HZSM-5 zeolites. • ZnOH + /BAS-HZSM−5 with the moderate acid strength is conducive to the formation of PX. The methylation reaction of methanol and toluene to xylenes has been carried out in Brønsted Acid Sites (BAS)−HZSM−5, AlOH 2+ /BAS−HZSM−5 and ZnOH + /BAS−HZSM−5 catalysts. The stronger acid strengths are produced in AlOH 2+ /BAS−HZSM−5 and ZnOH + /BAS−HZSM−5 due to the synergistic effect of Lewis Acid Sites (LAS) and BAS compared to BAS−HZSM−5, which is beneficial to the dissociation of methanol. AlOH 2+ /BAS−HZSM−5 shows the highest activity for methanol dissociation with the strongest acid strength. The Gibbs free energy barrier is only 68.2 kJ·mol −1 , but the formation of Para -xylene (PX) needs to overcome a high barrier of 129.2 kJ·mol −1 . However, ZnOH + /BAS−HZSM−5 exhibits relative high activity for the formation of methoxy with the Gibbs free energy barrier of 113.9 kJ·mol −1 , and 92.9 kJ·mol −1 for PX. Meanwhile, the formation of PX is easiest among three xylenes. Therefore, ZnOH + /BAS−HZSM−5 can be as the promising catalyst for the preparation of PX during methylation of toluene with methanol.

Selective synthesis of novel quinolones-amino esters as potential antibacterial and antifungal agents: Experimental, mechanistic study, docking and molecular dynamic simulations

A new selective synthesis of novel quinoline carboxamides was developed by the N-alkylation reaction of methyl (2-oxo-1,2- dihydroquinolin-4-yl)-l-alaninate via phase transfer catalysis in a basic medium at room temperature. The compounds were obtained in excellent yields (70–90%) and characterized by 1H, 13CNMR spectroscopy and mass spectra. In addition, theoretical studies at B3LYP/6–311G(d,p) level were carried out to explain the observed selectivity of the N-alkylation reaction of compound 2. The biological activities of the synthesized compounds were studied using some bacterial and fungal strains. The results show that compounds 3h and 3i exhibit stronger antibacterial activity against Bacillus subtilis and Staphyloccocus aureus. Compound 3e showed high antifungal activity against Candida Albicans compared to other substituted quinoline carboxamides. Molecular docking and molecular dynamics studies were also carried out to investigate the binding affinities of some compounds with the target proteins, and the results were in good correlation with the experimental findings.

Synthesis, Stability, and Diels‐Alder Reactions of Methyl 2‐Oxobut‐3‐enoate

AbstractMethyl vinyl glycolate (MVG, methyl 2‐hydroxybut‐3‐enoate) is a new biobased platform chemical, which is available by degradation of carbohydrates. In the present work, the oxidation of MVG to methyl 2‐oxobut‐3‐enoate has been investigated and a procedure developed with the Dess‐Martin periodinane. Methyl 2‐oxobut‐3‐enoate has not been characterized before and is stable for days at −18 °C, but slowly dimerizes by an unusual hetero‐Diels‐Alder reaction at room temperature. Therefore, the reactivity of methyl 2‐oxobut‐3‐enoate in the normal Diels‐Alder reaction with 1,3‐dienes has been investigated and a one‐pot procedure developed where MVG is first oxidized with the Dess‐Martin periodinane followed by the addition of the 1,3‐diene. A number of different 1,3‐dienes can take part in the cycloaddition to afford the functionalized cyclohexene products in moderate‐to‐good yields.

Metabolism and Regulatory Functions of O-Acetylserine, S-Adenosylmethionine, Homocysteine, and Serine in Plant Development and Environmental Responses.

The metabolism of an organism is closely related to both its internal and external environments. Metabolites can act as signal molecules that regulate the functions of genes and proteins, reflecting the status of these environments. This review discusses the metabolism and regulatory functions of O-acetylserine (OAS), S-adenosylmethionine (AdoMet), homocysteine (Hcy), and serine (Ser), which are key metabolites related to sulfur (S)-containing amino acids in plant metabolic networks, in comparison to microbial and animal metabolism. Plants are photosynthetic auxotrophs that have evolved a specific metabolic network different from those in other living organisms. Although amino acids are the building blocks of proteins and common metabolites in all living organisms, their metabolism and regulation in plants have specific features that differ from those in animals and bacteria. In plants, cysteine (Cys), an S-containing amino acid, is synthesized from sulfide and OAS derived from Ser. Methionine (Met), another S-containing amino acid, is also closely related to Ser metabolism because of its thiomethyl moiety. Its S atom is derived from Cys and its methyl group from folates, which are involved in one-carbon metabolism with Ser. One-carbon metabolism is also involved in the biosynthesis of AdoMet, which serves as a methyl donor in the methylation reactions of various biomolecules. Ser is synthesized in three pathways: the phosphorylated pathway found in all organisms and the glycolate and the glycerate pathways, which are specific to plants. Ser metabolism is not only important in Ser supply but also involved in many other functions. Among the metabolites in this network, OAS is known to function as a signal molecule to regulate the expression of OAS gene clusters in response to environmental factors. AdoMet regulates amino acid metabolism at enzymatic and translational levels and regulates gene expression as methyl donor in the DNA and histone methylation or after conversion into bioactive molecules such as polyamine and ethylene. Hcy is involved in Met–AdoMet metabolism and can regulate Ser biosynthesis at an enzymatic level. Ser metabolism is involved in development and stress responses. This review aims to summarize the metabolism and regulatory functions of OAS, AdoMet, Hcy, and Ser and compare the available knowledge for plants with that for animals and bacteria and propose a future perspective on plant research.