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

OBJECTIVETo investigate the effect of L-methionine (L-Met) on the content of Zn, Cu, Mn, Fe in liver, brain, spleen and kidney of lead intoxicated mice.

METHODSDistilled water was given to 10 mice (normal control group) and lead acetate solution of 400 micro g/ml Pb(2+) to 20 mice to serve as drinking water for 10 days. The lead administration was then withdrawn and lead exposed mice were randomly divided into two groups: the lead control group took distilled water as drinking water for 4 weeks to serve as positive control, the other one took L-Met solution (0.5 mg/ml) as drinking water for 4 weeks (Pb + L-Met group) to serve as the treatment group. All the animals were sacrificed on the 1st day after 4 weeks, and the contents of Zn, Cu, Fe, Mn, Pb in liver, brain, spleen and kidney were measured by Inductively Coupled Plasma (ICP) Emission Spectrometry.

RESULTSLead contents in liver, brain, spleen and kidney of Pb control group [(1.490 +/- 1.654) micro g/g, (3.470 +/- 2.757) micro g/g, (4.975 +/- 2.993) micro g/g, (0.066 +/- 0.001) micro g/g respectively], were higher than those in normal control group [(0.015 +/- 0.001) micro g/g, (0.009 +/- 0.007) micro g/g, (0.027 +/- 0.002) micro g/g, (0.006 +/- 0.015) micro g/g, P < 0.05] while Zn contents in liver, brain, spleen and Fe and Mn content in liver, brain, spleen and kidney in Pb control group were lower than those in normal control group (P < 0.05). Pb contents of brain, spleen and Cu content of kidney in Pb + L-Met group were higher than those in normal control group (P < 0.05). Zn contents of liver, brain, spleen, Fe contents of liver, brain, spleen, kidney, and Mn contents of brain, spleen in Pb + L-Met group were lower than those in normal control group (P < 0.05). Fe contents of liver, brain, Zn content of spleen, Cu content of kidney and Mn contents of liver, brain, spleen in the Pb + L-Met group were higher than those in the Pb control group (P < 0.05). The lead levels of four organs in the Pb + L-Met group were lower than those in the Pb control group (P < 0.05).

CONCLUSIONLead could be eliminated by L-Met, which may affect the distribution and metabolism of trace elements in mice.

Animals ; Brain ; metabolism ; Female ; Kidney ; metabolism ; Lead Poisoning ; metabolism ; Liver ; metabolism ; Male ; Methionine ; pharmacology ; Mice ; Spleen ; metabolism ; Trace Elements ; metabolism

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

Homocystinuria is an inborn error on the pathway of the methionine metabolism. It is mainly caused by a cystathionine B-synthase deficiency in the brain or liver. Homocystinuria is biochemically characterized by: 1) an increase of the homocystine and methionine concentration in the plasma; and 2) a decrease of the cystine with an increased excretion of homocystine in the urine. The clinical manifestations of this autosomal recessive disorder include: ectopoia lentis, skeletal abnormalities, high incidence of thromboembolism and high frequency of mental retardation. We have been experiencing a case of a 10 year old female patient who has suffered from homocystinuria. She has undergone mental retardation, poor vision caused by ocular complications and Marfanoid feautures.
Brain ; Child ; Cystathionine ; Cystine ; Ectopia Lentis* ; Female ; Homocystine ; Homocystinuria* ; Humans ; Incidence ; Intellectual Disability ; Liver ; Metabolism ; Methionine ; Plasma ; Thromboembolism

OBJECTIVE: To summarize newborn screening for methionine adenosyltransferase I/III (MAT I/III) deficiency in Quanzhou region of Fujian Province. METHODS: A total of 364 545 neonates were screened for inherited metabolic diseases by tandem mass spectrometry. High-throughput next generation sequencing combined with Sanger sequencing was used to detect potential variants in newborns with MAT I/III deficiency. Pathogenicity of suspected variants was predicted by using MutationTaster and HSF software. RESULTS: Three newborns were identified with MAT I/III deficiency by newborn screening, which yielded an incidence rate of 1 in 121 515. Amino acid and acylcarnitine analysis suggested that the serum methionine of the three patients have increased to various extents. All patients showed normal growth and development during follow-up, and were found to carry MAT1A gene variants including two missense variants [c.776C>T (p.Ala259Val) and c.791G>A (p.Arg264His)] and a synonymous variant [c.360C>T (p.Cys120Cys)]. Among these, c.776C>T (p.Ala259Val) and c.791G>A (p.Arg264His) were known to be pathogenic, whereas c.360C>T (p.Cys120Cys) was a novel variant. Bioinformatics analysis suggested that this variant may alter RNA splicing and affect the structure and function of the MAT1A protein. CONCLUSION A systematic review of newborn screening for MAT I/III deficiency was provided. Discovery of the novel variant has enriched the variant profile of the MAT1A gene and provided a basis for the diagnosis of this disease.
Amino Acid Metabolism, Inborn Errors ; diagnosis ; China ; Genetic Variation ; Humans ; Infant, Newborn ; Methionine Adenosyltransferase ; deficiency ; genetics ; Neonatal Screening

Animals ; Cadmium/toxicity* ; Dysbiosis/metabolism* ; Gastrointestinal Microbiome ; Glutamine/pharmacology* ; Methionine ; Mice ; Mice, Inbred C57BL ; Ostreidae ; Protein Hydrolysates ; Tyrosine

AIMTo explore the effect of hyperhomocysteinemia on vascular calcification and the underlying mechanism of it.

METHODSArterial calcification of Sprague-Dawley rats was induced by vitamin D3 plus nicotine. Hyperhomocysteinemia was established by feeding high methionine diet for six weeks and was assessed b y plasma total homocysteine (tHcy) level detected by HPLC method. Calcification was confirmed by von Kossa staining, measurement of calcium content, alkaline phosphatases (ALP) activity and osteocalcin (OC) concentration of vascular tissue. Lipid conjugated dienes formation were determined to reflecting the production of lipid peroxide.

RESULTSThe results showed that there were mass black granules deposited in aortic wall of the calcified rats by von Kossa staining. Calcium content, ALP activity, OC concentration in calcified rats increased by 8.09-fold, 45.57% and 2.81-fold compared with those of the control group (P < 0.01). Calcium content in calcified rats with high methionine diet increased by 34.29% compared with that of the calcified rats, while ALP activity and OC content decreased by 29.13% and 74.69% compared with that of the calcified rats. Lipid conjugated dienes formation in plasma of the rat with high methionine diet and of calcified rats with high methionine diet increased by 1.93 and 2.89-fold compared with those of the control group, respectively (P < 0.01), and in calcified rats with high methionine diet group was increased by 32.90% compared with that of high methionine diet group (P < 0.01).

CONCLUSIONHyperhomocysteinemia could promote vascular calcification, which might be mediated through the production of lipid peroxide.

Alkaline Phosphatase ; metabolism ; Animals ; Calcium ; metabolism ; Endothelium, Vascular ; Hyperhomocysteinemia ; metabolism ; pathology ; Lipid Peroxidation ; Male ; Methionine ; administration & dosage ; Osteocalcin ; analysis ; Rats ; Rats, Sprague-Dawley ; Vascular Calcification ; metabolism ; pathology

OBJECTIVETo explore the role of glial cell metabolism in the generation and regulation of central respiratory rhythm.

METHODSThe medulla oblongata slices (600-700 microm) containing the medial region of the nucleus retrofacialis (mNRF) with the hypoglossal nerve rootlets retained from 12 neonatal (0-3 days) Sprague-Dawley rats were prepared and perfused with modified Kreb's solution (MKS). Upon recording of respiratory rhythmical discharge activity (RRDA) of the rootlets of the hypoglossal nerve, the brain slices were treated with glial cell metabolism antagonist L-methionine sulfoximine (L-MSO, 50 micromol/L) for 20 min followed by application of glial cell metabolism agonist L-glutamine (L-GLN, 30 micromol/L) for 20 min, or with L-MSO for 20 min with additional L-GLN for 20 min. The changes in the RRDA of the rootlets of the hypoglossal nerve in response to the treatments were recorded.

RESULTSL-MSO prolonged the respiratory cycle (RC) and expiratory time (TE), and reduced the integral amplitude (IA) and the inspiratory time (TI) in the brain slices. L-GLN induced a significant decrease in RC and TE, but IA and TI showed no obvious variations. The effect of L-MSO on the respiratory rhythm was reversed by the application of L-GLN.

CONCLUSIONGlial cell metabolism may play an important role in the modulation of RRDA in neonatal rat brainstem.

Animals ; Animals, Newborn ; Glutamine ; pharmacology ; In Vitro Techniques ; Medulla Oblongata ; metabolism ; physiology ; Methionine Sulfoximine ; pharmacology ; Neuroglia ; metabolism ; Periodicity ; Rats ; Rats, Sprague-Dawley ; Respiration