Methylation plays a vital role in biological systems. SAM (S-adenosyl-L-methionine), an abundant cofactor in life, acts as a methyl donor in most biological methylation reactions. SAM-dependent methyltransferases (MTase) transfer a methyl group from SAM to substrates, thereby altering their physicochemical properties or biological activities. In recent years, many SAM analogues with alternative methyl substituents have been synthesized and applied to methyltransferases that specifically transfer different groups to the substrates. These include functional groups for labeling experiments and novel alkyl modifications. This review summarizes the recent progress in the synthesis and application of SAM methyl analogues and prospects for future research directions in this field.
S-Adenosylmethionine/metabolism* ; Methionine ; Methyltransferases/metabolism* ; Methylation ; Racemethionine

No abstract available.
Methionine*

To utilize Pichia pastoris to produce S-adenosyl-L-methionine (SAM), an intracellular expression vector harboring S. cerevisiae SAM2 was transformed into GS115. A recombinant strain having 2 copies of expression cassette was obtained through G418 resistance screening. This strain had higher SAM synthetase activity and higher SAM production capacity than the original strain, when cultured in medium containing methanol and methionine. The carbon source and nitrogen source of medium was optimized. The results showed SAM production by this strain was closely related to carbon metabolism. With supplementation of 0.2% glycerol every day from the beginning of 3rd day, this strain produced 1.58 g/L SAM when cultured in a medium containing 0.75% L-methionine and optimized carbon and nitrogen source after 6 days.
Methionine Adenosyltransferase ; genetics ; metabolism ; Pichia ; genetics ; Recombinant Proteins ; metabolism ; S-Adenosylmethionine ; biosynthesis

The yield of S-adenosyl-L-methionine (SAM) on high-cell-density fermentation by saccharomyces cerevisiae is mostly affected by the feeding strategy of pre-L-methionine. The mutant strain SAM0801 that could accumulate more SAM was used in this study. Six high-cell-density fermentation experiments in 5 L fermentor were investigated to get the optimal feeding time and amount of L-methionine. The results showed that when 40 g L-methionine was added in the fermentor after 30 h fermentation, a dry cell weight of 100 g/L was achieved. Under this condition, after 58 h fermentation, both the dry cell weight and the yield of SAM reached the maximum, 168 g/L and 14.48 g/L respectively.
Bioreactors ; microbiology ; Fermentation ; Methionine ; analysis ; metabolism ; Mutation ; S-Adenosylmethionine ; biosynthesis ; Saccharomyces cerevisiae ; genetics ; growth & development ; metabolism

The yield of S-adenosyl-L-methionine (SAM) by saccharomyces cerevisiae fermentation was affected by the strategy of feeding L-methionine. The effects that feeding strategies and the amount of precursor L-methionine had on the production of SAM by saccharomyces cerevisiae G14 were investigated. The results showed that feeding L-methionine could obviously improve the accumulation of SAM, and both the biomass and SAM yield relied heavily on different feeding strategies. In our work, it was found that total amount of L-methionine added should be no less than 0.7g per 10 grams of dry cell weight. Five different feeding strategies had been investigated in our experiment, and such comparison indicated that favorable results could be achieved as the biomass reached the status of high cell density (120g/L). If 9 grams of the precursor L-methionine was introduced once and for all, the accumulation of SAM reached maximum of 4.31g/L at the 18th hour after addition; if the precursor amino acid was fed at a rate of 2g/h in 5 h, maximum yield of 4.98g/L was achieved at the 28th hour after feeding. Thus high cell density fermentation can be successfully applied to SAM production by Saccharomyces cerevisiae with the consequence of over 130g/L of biomass gained using the above two strategies.
Bioreactors ; microbiology ; Cell Culture Techniques ; methods ; Culture Media ; Fermentation ; Methionine ; metabolism ; S-Adenosylmethionine ; biosynthesis ; Saccharomyces cerevisiae ; growth & development ; metabolism

Golgi SNAP receptor complex 1 (GS28) has been implicated in vesicular transport between intra-Golgi networks and between endoplasmic reticulum (ER) and Golgi. Additional role(s) of GS28 within cells have not been well characterized. We observed decreased expression of GS28 in rat ischemic hippocampus. In this study, we examined the role of GS28 and its molecular mechanisms in neuronal (SK-N-SH) cell death induced by hydrogen peroxide (H2O2). GS28 siRNA-transfected cells treated with H2O2 showed a significant increase in cytotoxicity under glutathione (GSH)-depleted conditions after pretreatment with buthionine sulfoximine, which corresponded to an increase of intracellular reactive oxygen species (ROS) in the cells. Pretreatment of GS28 siRNA-transfected cells with p38 chemical inhibitor significantly inhibited cytotoxicity; we also observed that p38 was activated in the cells by immunoblot analysis. We confirmed the role of p38 MAPK in cotransfected cells with GS28 siRNA and p38 siRNA in the cell viability assay, flow cytometry, and immunoblot. Involvement of apoptotic or autophagic processes in the cells was not shown in the cell viability, flow cytometry, and immunoblot analyses. However, pretreatment of the cells with necrostatin-1 completely inhibited H2O2-induced cytotoxicity, ROS generation, and p38 activation, indicating that the cell death is necroptotic. Collectively these data imply that H2O2 induces necroptotic cell death in the GS28 siRNA-transfected cells and that the necroptotic signals are mediated by sequential activations in RIP1/p38/ROS. Taken together, these results indicate that GS28 has a protective role in H2O2-induced necroptosis via inhibition of p38 MAPK in GSH-depleted neuronal cells.
Animals ; Buthionine Sulfoximine ; Cell Death ; Cell Survival ; Endoplasmic Reticulum ; Flow Cytometry ; Glutathione ; Hippocampus ; Hydrogen ; Hydrogen Peroxide ; Imidazoles ; Indoles ; Methionine ; Neurons ; p38 Mitogen-Activated Protein Kinases ; Rats ; Reactive Oxygen Species ; RNA, Small Interfering ; SNARE Proteins

Circadian Clocks/genetics* ; Reactive Oxygen Species ; Methionine ; Gastrointestinal Microbiome ; Gastrointestinal Tract ; Racemethionine ; Gene Expression

OBJECTIVETo investigate whether or not lipopolysaccharide (LPS) and ovalbumin (OA) prime rat peripheral leukocytes, the effect of sensitization on priming and the role of phospholipase D in priming.

METHODSThe peripheral leukocytes were separated and purified from sensitized or unsensitized rats. LPS or OA was used as a priming agent and formylmethionylphenylalanine (fMLP) as an activating agent. Degradation of leukocyte was determined by measurement of elastase release and myeloperoxidase (MPO) activity. Phospholipase D (PLD) activity was assayed by the generation of choline,which was measured by choline-oxidase-catalyzed formation of H(2)O(2) and Trinder reaction.

RESULTCompared with cells treated by fMLP alone,leukocytes from unsensitized rat challenged with fMLP after incubated with LPS released more elastase and MPO (P<0.05). But there was no significant difference between leukocytes challenged with fMLP after incubated with OA and fMLP treated alone. In sensitized rat,there was no difference between leukocytes challenged with fMLP after incubated with LPS and fMLP treated alone. But leukocytes challenged with fMLP after incubated with OA released significantly more elastase and MPO than fMLP treated alone (P<0.05). A significant correlation was obtained between the release of elastase and PLD activity (r(s)=0.51,P<0.01), and also between the release of MPO and PLD activity (r(s)=0.73,P<0.01) in unsensitized rat. In sensitized rat, it was 0.48 (P<0.01) and 0.37 (P<0.05) respectively.

CONCLUSION(1) LPS primes peripheral leukocytes from unsensitized rats; (2) OA primes peripheral leukocytes from actively sensitized rats; (3) PLD plays a role in priming of rat peripheral leukocytes.

Animals ; Leukocyte Elastase ; secretion ; Leukocytes ; drug effects ; enzymology ; Lipopolysaccharides ; pharmacology ; Male ; N-Formylmethionine Leucyl-Phenylalanine ; pharmacology ; Ovalbumin ; immunology ; Peroxidase ; blood ; Phospholipase D ; physiology ; Rats ; Rats, Sprague-Dawley

Folate is generally considered as a safe water-soluble vitamin for supplementation. However, we do not have enough information to confirm the potential effects and safety of folate supplementation and the interaction with vitamin B12 deficiency. It has been hypothesized that a greater methyl group supply could lead to compensation for vitamin B12 deficiency. On this basis, the present study was conducted to examine the effects of high-dose folic acid (FA) supplementation on biomarkers involved in the methionine cycle in vitamin B12-deficient rats. Sprague-Dawley rats were fed diets containing either 0 or 100 microg (daily dietary requirement) vitamin B12/kg diet with either 2 mg (daily dietary requirement) or 100 mg FA/kg diet for six weeks. Vitamin B12-deficiency resulted in increased plasma homocysteine (p<0.01), which was normalized by dietary supplementation of high-dose FA (p<0.01). However, FA supplementation and vitamin B12 deficiency did not alter hepatic and brain S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) concentrations and hepatic DNA methylation. These results indicated that supplementation of high-dose FA improved homocysteinemia in vitamin B12-deficiency but did not change SAM and SAH, the main biomarkers of methylating reaction.
Animals ; Biomarkers ; Brain ; Compensation and Redress ; Diet ; Dietary Supplements ; DNA Methylation ; Folic Acid ; Homocysteine ; Hyperhomocysteinemia ; Methionine ; Plasma ; Rats ; Rats, Sprague-Dawley ; S-Adenosylhomocysteine ; S-Adenosylmethionine ; Vitamin B 12 Deficiency ; Vitamins

BACKGROUND/OBJECTIVE: The aim of this study was to examine the effect of high dietary methionine (Met) consumption on plasma and hepatic oxidative stress and dyslipidemia in chronic ethanol fed rats. MATERIALS/METHODS: Male Wistar rats were fed control or ethanol-containing liquid diets supplemented without (E group) or with DL-Met at 0.6% (EM1 group) or 0.8% (EM2 group) for five weeks. Plasma aminothiols, lipids, malondialdehyde (MDA), alanine aminotransferase (ALT), and aspartate aminotransferase were measured. Hepatic folate, S-adenosylmethionine (SAM), and S-adenosylhomocysteine (SAH) were measured. RESULTS: DL-Met supplementation was found to increase plasma levels of homocysteine (Hcy), triglyceride (TG), total cholesterol (TC), and MDA compared to rats fed ethanol alone and decrease plasma ALT. However, DL-Met supplementation did not significantly change plasma levels of HDL-cholesterol, cysteine, cysteinylglycine, and glutathione. In addition, DL-Met supplementation increased hepatic levels of folate, SAM, SAH, and SAM:SAH ratio. Our data showed that DL-Met supplementation can increase plasma oxidative stress and atherogenic effects by elevating plasma Hcy, TG, and TC in ethanol-fed rats. CONCLUSION: The present results demonstrate that Met supplementation increases plasma oxidative stress and atherogenic effects by inducing dyslipidemia and hyperhomocysteinemia in ethanol-fed rats.
Alanine Transaminase ; Animals ; Aspartate Aminotransferases ; Cholesterol ; Cysteine ; Diet ; Dyslipidemias* ; Ethanol ; Folic Acid ; Glutathione ; Homocysteine ; Humans ; Hyperhomocysteinemia ; Male ; Malondialdehyde ; Methionine* ; Oxidative Stress* ; Plasma ; Rats* ; Rats, Wistar ; S-Adenosylhomocysteine ; S-Adenosylmethionine ; Triglycerides