SEARCH · PubMed Health

Results for “METHIONINE”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed1984

Portal and vena caval plasma methionine concentrations in young pigs administered L-methionine, N-acetyl-L-methionine and N-acetyl-D-methionine.

N-Acyl-methionine derivatives have been proposed as replacements for methionine in supplementing food products low in this amino acid. We studied the effects of N-acetyl-L-methionine, N-acetyl-D-methionine and L-methionine loads (2 mmol/kg body weight) on portal and vena caval plasma amino acid concentrations in young pigs (n = 4). L-Methionine loading significantly increased mean (+/- SD) portal and vena caval plasma methionine concentrations from baseline values of 6.44 +/- 1.03 and 6.63 +/- 0.99 mumol/100 ml, respectively, to mean peak values of 340 +/- 75.0 and 265 +/- 49.8 mumol/100 ml, respectively. N-Acetyl-L-methionine loading increased mean peak portal and vena caval plasma methionine concentrations to 291 +/- 85 and 220 +/- 51.6 mumol/100 ml, respectively. N-Acetyl-L-methionine could not be detected in either portal or vena caval plasma. In contrast, N-acetyl-D-methionine loading produced only a small rise in mean peak portal and vena caval plasma methionine concentrations (13.0 +/- 4.31 and 8.62 +/- 1.71 mumol/100 ml, respectively). Concentrations of N-acetyl-D-methionine increased from baseline values of 0 mumol/100 ml to mean peak values of 251 +/- 32.0 and 234 +/- 72.3 mumol/100 ml, respectively, in portal and vena caval plasma. These data explain the poor utilization of N-acetyl-D-methionine as a methionine source.

Animals↗

PubMed1986

Effects of equimolar doses of L-methionine, D-methionine and L-methionine-dl-sulfoxide on plasma and urinary amino acid levels in normal adult humans.

Plasma and urinary amino acid levels were measured in four normal adult subject administered equimolar quantities (0.0605 mmol/kg body wt) of L-methionine, D-methionine and L-methionine-dl-sulfoxide in a randomized crossover design. Plasma total methionine concentrations increased significantly (P less than 0.05) over base line (3.7 +/- 1.2 mumol/dl; mean +/- SD) after loading with each compound. Mean peak plasma methionine levels were 9.8 +/- 1.1, 14.4 +/- 2.3 and 5.2 +/- 1.0 mumol/dl after loading with L-methionine, D-methionine and L-methionine sulfoxide, respectively. D-Methionine accounted for the increased plasma levels seen after D-methionine loading. None of the three compounds affected plasma cystine, cysteine or taurine concentrations. Plasma methionine sulfoxide concentrations were not affected by loading with D- or L-methionine but increased significantly after ingestion of L-methionine sulfoxide. Urinary methionine excretion was 20 times higher after ingestion of D-methionine than after ingestion of L-methionine or L-methionine sulfoxide, with the increase due to D-methionine excretion. Urinary excretion of methionine sulfoxide and its N-acetyl derivatives was not significantly higher after loading with methionine sulfoxide. The data indicate that adult humans do not utilize D-methionine efficiently as a methionine source but probably do utilize L-methionine-dl-sulfoxide.

Adult↗

PubMed1980

Plasma methionine levels in normal adult subjects after oral loading with L-methionine and N-acetyl-L-methionine.

The biological quality of soy protein isolates is limited by methionine content but can be enhanced by methionine addition. Since supplemental methionine may undergo chemical modification during processing, producing objectionable odors, N-acetyl-L-methionine has been proposed as a methionine replacement. Plasma and erythrocyte methionine levels and the area under the plasma and erythrocyte methionine absorption curve were compared in five normal adult subjects administered equimolar quantities (0.0605 mmoles/kg) of L-methionine and N-acetyl-L-methionine. The two compounds produced an equivalent overall release of L-methionine to the blood as judged by the area under the plasma and erythrocyte methionine time-absorption curves. There was a difference in the early part of both absorption curves (15 to 45 minutes), with plasma and erythrocyte levels higher after L-methionine administration than after N-acetyl-L-methionine administration. However, this difference was only statistically significant at 15 minutes (P = 0.03). Gastric emptying did not account for this difference apparently reflecting a slower rate of absorption of N-acetyl-L-methionine by mucosal cells. No evidence was obtained that indicated release of N-acetyl-L-methionine to the plasma or its excretion in urine after loading. The data are consistent with previous data showing L-methionine and N-acetyl-L-methionine to be equivalent sources of methionine.

Adult↗

PubMed2003

Selective solid-phase isolation of methionine-containing peptides and subsequent matrix-assisted laser desorption/ionisation mass spectrometric detection of methionine- and of methionine-sulfoxide-containing peptides.

Methionine residues and the oxidised forms in proteins are becoming more and more important in view of their biological function. In particular, methionine sulfoxide seems to have a regulatory function. This paper presents a fast strategy for simultaneous determination of methionine- and methionine-sulfoxide-containing peptides, involving application of methionine-specific solid-phase reagent chemistry combined with matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS). In the first step, methionine-containing peptides are covalently bound as sulfonium salts to glass beads, whereas methionine-sulfoxide-containing peptides and other methionine-free peptides are not bound and are washed out. The wash solution is used for MALDI-MS analysis to determine the molecular masses of these peptides and to perform, if necessary, seamless post-source decay (PSD) fragment ion analysis. Methionine-sulfoxide-containing peptides can be identified due to the characteristic metastable loss of methanesulfenic acid from the protonated molecules. In the second step, the bound peptides are cleaved from the matrix of the beads by addition of 2-mercaptoethanol at pH 8.5-8.8. The resulting peptides, mainly methionine-containing peptides, are analysed in a straightforward manner by MALDI-MS and seamless PSD. The strategy allows the fast identification of methionine- and methionine-sulfoxide-containing peptides even in complex tryptic digests, as demonstrated here for the glycoprotein antithrombin. These results show that sometimes methionine-containing tryptic peptides are not detected due to steric restrictions (e.g. glycosylation near the methionine residue) on the binding reaction, and that, on the other hand, some methionine-free peptides can be quite strongly bound non-covalently to the matrix of the beads. The latter observation indicates the necessity of seamless PSD fragment ion analysis for unambiguous identification. Furthermore, there are indications that oxidation of some methionine residues occurred to a minor extent during the solid-phase isolation steps.

Humans↗

PubMed1982

Plasma and urinary methionine levels in one-year-old infants after oral loading with L-methionine and N-acetyl-L-methionine.

N-acetyl-L-methionine has been proposed as a replacement for methionine in supplementing food products low in this amino acid. Previous studies in adult subjects administered equimolar quantities (0.0605 mmoles/kg body weight) of L-methionine and N-acetyl-L-methionine showed equivalent overall release of methionine to the blood as judged by area under the plasma methionine time--absorption curve. In the present study, similar doses (0.0605 mmoles/kg body weight) of L-methionine and N-acetyl-L-methionine were administered to fasting 1-year-old infants in a randomized crossover design. The two compounds produced an equivalent overall release of methionine to the blood as judged by plasma methionine concentrations and by the area under the plasma methionine concentration--time curves. No evidence was obtained that indicated release of N-acetyl-L-methionine to plasma or its excretion in urine after loading. However, peak plasma methionine concentrations, and the areas under the plasma methionine concentration--time curves for infants were approximately one-half the values observed in normal adults administered equimolar doses of each compound on a per kilogram body weight basis. The data suggest more rapid metabolism of methionine and N-acetyl-L-methionine by infants than adults.

Age Factors↗

PubMed1986

Salvage of 5'-deoxy-5'-methylthioadenosine and L-homocysteine into methionine in cells cultured in a methionine-free medium: a study of "methionine-dependence".

The metabolism of the two methionine precursors, L-homocysteine and 5'-deoxy-5'-methylthioadenosine was compared to the ability of these compounds to support cell growth in a Met-free medium, in the following mammalian cell lines: Raji, CCL 39 and BHK cells. These three cell lines metabolized L-homocysteine and 5'-deoxy-5'-methylthioadenosine into methionine, S-adenosyl-L-methionine and proteins. However there was a discrepancy between metabolic and growth studies: Raji cells could grow on L-homocysteine and on 5'-deoxy-5'-methylthioadenosine, BHK cells could grow on L-homocysteine but not on 5'-deoxy-5'-methylthioadenosine, and CCL 39 cells could not grow either on L-homocysteine or on 5'-deoxy-5'-methylthioadenosine. The metabolism of exogenous methionine, and of methionine endogenously synthesized from 5'-deoxy-5'-methylthioadenosine was studied in CCL 39 and Raji cells, incubated with 25 microM [methyl-14c] methionine + 25 microM 5'-deoxy-5'-methylthioadenosine or 25 microM [methyl-14c] 5'-deoxy-5'-methylthioadenosine + 25 microM methionine: there was no difference between the metabolism of exogenous and endogenous methionine in either type of cell. Our results indicate that i) "methionine dependence" initially described for L-homocysteine [Hoffman, R.M. and Erbe, R.W. (1976) Proc. Natl. Acad. Sci. USA 73, 1523], can also be observed with the other precursor of methionine, ie 5'-deoxy-5'-methylthioadenosine; ii) "methionine-dependence" can not be considered as the inability of a cell to grow on methionine endogenously synthesized from a precursor, but depends on the precursor used, and possibly, on a toxic effect of the precursor in the absence of methionine.

Adenosine↗

PubMed1983

Reduced free-methionine in methionine-dependent SV40-transformed human fibroblasts synthesizing apparently normal amounts of methionine.

Many different types of cancer cells have been shown to be methionine-dependent. These cells, unlike normal cells, grow poorly or not at all when methionine is replaced by its immediate precursor homocysteine in the growth medium (Met- Hcy+ medium). We have previously shown that apparently normal total amounts of methionine are synthesized by methionine-dependent SV40-transformed human fibroblasts. However, methionine-dependent cells in Met- Hcy+ medium accumulate reduced amounts of S-adenosylmethionine (AdoMet) and elevated amounts of S-adenosylhomocysteine (AdoHcy) that together probably limit growth. In this report, we demonstrate that the amount of free methionine is low in methionine-dependent SV40-transformed human fibroblasts in Met- Hcy+ medium compared to normal human diploid fibroblasts. In contrast, in Met+ Hcy- medium, the amount of free methionine is comparable in both cell types. The deficient pool of free methionine in methionine-dependent cells in Met- Hcy+ medium allows only low amounts of AdoMet to be formed. However, large amounts of the biosynthesized methionine are channeled into protein synthesis. Possible mechanisms are discussed to explain this cancer-associated metabolic defect.

Cell Line↗

PubMed1992

Brain protein synthesis in the conscious rat using L-[35S]methionine: relationship of methionine specific activity between plasma and precursor compartment and evaluation of methionine metabolic pathways.

The method previously developed for the measurement of rates of methionine incorporation into brain proteins assumed that methionine derived from protein degradation did not recycle into the precursor pool for protein synthesis and that the metabolism of methionine via the transmethylation pathway was negligible. To evaluate the degree of recycling, we have compared, under steady-state conditions, the specific activity of L-[35S] methionine in the tRNA-bound pool to that of plasma. The relative contribution of methionine from protein degradation to the precursor pool was 26%. Under the same conditions, the relative rate of methionine flux into the transmethylation cycle was estimated to be 10% of the rate of methionine incorporation into brain proteins. These results indicate the following: (a) there is significant recycling of unlabeled methionine derived from protein degradation in brain; and (b) the metabolism of methionine is directed mainly towards protein synthesis. At normal plasma amino acid levels, methionine is the amino acid which, to date, presents the lowest degree of dilution in the precursor pool for protein synthesis. L-[35S]-Methionine, therefore, presents radiobiochemical properties required to measure, with minimal underestimation, rates of brain protein synthesis in vivo.

Animals↗

PubMed1987

Effect of fasting and of methionine deficiency on L-methionine, DL-methionine and DL-2-hydroxy-4-methylthiobutanoic acid metabolism in broiler chicks.

Metabolism of L-[1-14C]methionine, DL-[1-14C]methionine and DL-[1-14C]2-hydroxy-4-methylthiobutanoic acid (DL-HMB) by broiler chicks which had been fasted overnight or given a methionine-deficient diet was compared with fed (control) birds. The excretion of 14C-labelled material, total 14CO2 exhaled, 14C incorporation into tissue proteins and the 14C-labelled material in perchloric-acid-soluble tissue fractions were measured 6 h after injection of the 14C-labelled materials. The incorporation of 14C into tissue proteins and the relative rates of conversion of D-methionine and DL-HMB to L-methionine in tissues under different nutritional regimens were compared using protein-bound 14C:protein-free 14C values. Fasted birds exhaled more 14CO2 than control birds but excreted less 14C, while methionine-deficient birds behaved very similarly to the control animals in these respects. Fasted birds incorporated much less 14C into proteins of tissues other than liver and kidney from all three labelled tracers. The values for protein-bound 14C:protein-free 14C were lower in all tissues. Methionine-deficient birds had similar levels of 14C in tissue proteins but lower values for protein bound 14C:protein-free 14C. Examination of the values for protein-bound 14C:protein-free 14C suggest that brain and probably liver tissues from fasted and methionine-deficient birds showed improved rates of conversion of D-methionine and DL-HMB to L-methionine compared with control animals.

Animals↗

PubMed2004

Oxidation of methionine residues in aqueous solutions: free methionine and methionine in granulocyte colony-stimulating factor.

The free energy barriers and a mechanism of the oxidation of the amino acid methionine in water and in granulocyte colony-stimulating factor (G-CSF) are analyzed via combined quantum mechanical and molecular mechanical (QM/MM) methods, constrained molecular dynamics, and committor probability calculations. The computed free energy barrier of free methionine amino acid is very close to the measured value (14.7 +/- 1.2 versus 15.5 +/- 0.02 kcal/mol). The reaction coordinate was found to be the difference between the O-O bond of H2O2 and the S-O bond, where the S is the sulfur atom of the methionine residue. It was confirmed by computing the committor probability distribution and the distribution of constrained forces that this coordinate is not coupled to the activation of other degrees of freedom. The computed free energies of the oxidation of methionine residues in G-CSF indicate that the protein environment has insignificant effects on the reaction barriers of oxidation. This result further validates our proposal that the access of solvent to methionine sites, as measured by the two-shell water coordination number, governs the kinetics of the oxidation reaction of methionine groups in a protein molecule. We also found that the number of hydrogen bonds between the distal oxygen of H2O2 and the water molecules near the methionine increases along the reaction coordinate as oxidation progresses, indicating that the charge separation developed during the oxidation by H2O2 is stabilized by specific interactions with water molecules, such as hydrogen bonding.

Granulocyte Colony-Stimulating Factor↗

PubMed1978

Utilization of dietary sulfur compounds by fingerling channel catfish: L-methionine, DL-methionine, methionine hydroxy analogue, taurine and inorganic sulfate.

Sixteen isonitrogenous, isoenergetic diets were fed to fingerling channel catfish to study the efficacy of L-methionine, DL-methionine, methionine hydroxy analogue (OH-M), taurine and sodium sulfate. The basal diet contained casein and gelatin supplemented with crystalline L-amino acids to correspond to the amino acid pattern found in 24% crude protein from whole egg powder. The basal diet, containing 0.26% methionine was supplemented with graded levels of each of the sulfur sources on an isosulfurous basis. Growth and feed efficiency data indicate that channel catfish can utilize DL-methionine as effectively as L-methionine. OH-M was only about 26% as effective in promoting growth as L-methionine. No significant growth response was observed when taurine or inorganic sulfate was added to the basal diet.

Amino Acids↗

PubMed1990

Antiinflammatory activity of methionine, methionine sulfoxide and methionine sulfone.

The oxidation of methionine in peptides is often associated with the loss of biological activity. Since methionine showed good antiinflammatory activity, its oxidized products methionine sulfoxide and methionine sulfone were tested. The sulfone was more active than the sulfoxide although methionine was most active indicating that the antiinflammatory activity is not correlated with the oxidation state of sulphur. Their hydroxyl radical scavenging activity was measured. Methionine was most active and sulfone was least active. Here also no correlation with antiinflammatory activity was found.

Animals↗

PubMed1988

Patterns of methionine auxotrophy in normal and neoplastic cells: the methionine independence of lymphocyte mitogenesis and low frequency of the methionine-dependent phenotype in human tumors.

Seven murine and 17 human tumor-derived cell lines were tested for their ability to grow in methionine-free medium containing the methionine precursor homocysteine. Three murine tumors, SP1, MDAY-D2, and L1210, failed to grow in this medium and were therefore methionine dependent (Met-Dep). In contrast, all human tumors, including 8 recently established cell lines, were methionine independent (Met-Indep). Concanavalin A-induced lymphocyte mitogenesis was also Met-Indep but required 3 to 4 times the amount of homocysteine needed for the growth of normal fibroblasts or Met-Indep tumors. In addition, lymphocyte mitogenesis was also supported by exogenous 5'-methylthioadenosine, another methionine precursor formed during polyamine synthesis. In contrast, Met-Dep tumors did not respond to increasing homocysteine concentration, nor was their growth supported by 5'-methylthioadenosine. These findings demonstrate that Met-Dep can occur by varied mechanisms relating to such parameters as homocysteine concentration and the ability of cells to generate Met-Indep revertants or to grow in 5'-methylthioadenosine. In general, we found the Met-Dep phenotype to be more common in murine tumor cells and to occur infrequently in human tumors. This may imply a species difference in methionine metabolism.

Adenosine↗

PubMed1985

Response of broilers to DL-methionine hydroxy analog free acid, DL-methionine, and L-methionine.

An experiment was designed to compare graded levels of DL-methionine hydroxy analog, free acid, 88% in aqueous solution; 2-hydroxy-4-(methylthio)butanoic acid (HMB), the aqueous solution of the sodium salt of DL-methionine (40%) (DLM), and crystalline L-methionine (LM) as sources of supplemental methionine activity. The experiment utilized 2160 broilers of each sex grown in separate pens to 7 weeks of age with a lysine-supplemented corn-soybean meal basal diet. These supplements produced a maximum 15% growth response over the unsupplemented basal diet. There were no statistically significant differences among the three sources in producing weight gain and feed conversion. There were no source X level interactions with regard to body weight gain. There was one source X level interaction (at 7 weeks) for feed conversion. The results support the conclusion that when synthetic sources of methionine activity are used to meet the requirement for total sulfur amino acids in practical corn-soybean meal diets for producing 7-week-old broilers, the chicks are capable of utilizing HMB, DLM, and LM with an efficiency that is indistinguishable.

Animals↗

PubMedDate not supplied

[The effect of DL-methionine, N-hydroxymethyl-DL-methionine calcium salt (Mepron) and DL-methionine hydroxy analog calcium salt (MHA) on the N-deposits of calves].

Digestibility and N balance experiments with calves showed that the methionine requirement of the host animal is covered by microbial protein synthesis even in the already ruminant animal. A supplement of the ration with DL methionine is only effective when it is provided in milk replacer. The MHA substitution of the ration has only little influence on N retention, independent of its supply in milk replacer or concentrated feed. MEPRON proved to be the most effective methionine derivative. As supplement both with the fluid feed and with the concentrated feed this compound shows exclusively positive results even in already ruminant calves with regard to live weight gain, N retention and the content of free methionine in the blood serum of the test animals.

Animal Feed↗

PubMed1983

Parallel distribution of methionine-enkephalin-Arg6-Gly7-Leu8 with methionine-enkephalin, leucine-enkephalin and methionine-enkephalin-Arg6-Phe7 in human and bovine brains.

Using specific radioimmunoassays(RIAs) for methionine-enkephalin(Met-Enk), leucine-enkephalin(Leu-Enk), methionine-enkephalin-Arg6-Gly7-Leu8 (Met-Enk-Arg-Gly-Leu) and methionine-enkephalin-Arg6-Phe7 (Met-Enk-Arg-Phe), we studied the regional distribution of these opioid peptides in human and bovine brains. Met-Enk-Arg-Gly-Leu was distributed in parallel with Met-Enk, Leu-Enk and Met-Enk-Arg-Phe in human and bovine brains. The ratios of molar concentrations of these peptides are almost constant in various regions of human and bovine brains and similar to the ratio of these peptides contained in preproenkephalin A. Gel exclusion chromatography and HPLC coupled with respective RIAs showed the existence of authentic peptides without any detectable high molecular weight forms. These results indicate the parallel distribution of Met-Enk-Arg-Gly-Leu with Met-Enk, Leu-Enk and Met-Enk-Arg-Phe in various regions of human and bovine brains and further suggest that these opioid peptides are derived from the same precursor as that in the adrenal medulla and that the processing of preproenkephalin A is almost complete in human and bovine brains.

Animals↗

PubMed1983

Methionine-enkephalin, leucine-enkephalin methionine-enkephalin-Arg6-Phe7 and methionine-enkephalin-Arg6-Gly7-Leu8 in human pheochromocytoma.

Methionine-enkephalin(met-enkephalin)-, leucine-enkephalin(leu-enkephalin)-, methionine-enkephalin-Arg6-Phe7(met-enkephalin-Arg-Phe)- and methionine-enkephalin-Arg6-Gly7-Leu8(met-enkephalin-Arg-Gly-Leu)-like immunoreactivities(-LI) were studied in 16 pheochromocytomas by radioimmunoassays (RIAs) for these four opioid peptides. Met-enkephalin-Arg-Phe-LI and met-enkephalin-Arg-Gly-Leu-LI existed together with met-enkephalin-LI and leu-enkephalin-LI in 16 pheochromocytomas. Significant positive correlations were observed among contents of these four opioid peptides in 16 pheochromocytomas. The concentrations of these four opioid peptides in epinephrine producing pheochromocytomas were much higher than those in norepinephrine producing tumors. HPLC and gel exclusion chromatography followed by the RIAs showed the presence of met-enkephalin, leu-enkephalin, met-enkephalin-Arg-Phe and met-enkephalin-Arg-Gly-Leu together with their high molecular weight forms. These results indicate the co-existence of met-enkephalin, leu-enkephalin, met-enkephalin-Arg-Phe, met-enkephalin-Arg-Gly-Leu and their high molecular weight forms derived from preproenkephalin A in human pheochromocytomas and suggest the association of preproenkephalin A synthesis with epinephrine production in human pheochromocytomas.

Adrenal Gland Neoplasms↗

PubMed1976

Nitrogen retention in men fed isolated soybean protein supplemented with L-methionine, D-methionine, N-acetyl-L-methionine, or inorganic sulfate.

The ability of various sulfur-containing compounds to replace L-methionine (L-Met) was investigated by metabolic balance studies in man. N-acetyl-L-Methionine (AcMet), D-methionine (D-Met), and sodium sulfate (Na2SO4) were used to supplement a diet deficient in sulfur amino acids. The daily diet contained 4.5 g nitrogen (N) from isolated soybean protein (SB) and 4.5 g from glycine and alanine (9 g total N). SB diet was given alone or supplemented to six adult men for periods of 9 days after a standardization period with an equal N eggwhite diet, preceded by a 2-day zero N adaptation period. Supplements provided equivalent amounts of sulfur to that present in 420 ml L-Met, the amount added to SB to bring the total sulfur amino acid content to 900 mg/day. AcMet was as benfeficial as L-Met in improving N balance but D-Met was not as effective as L-Met. Difference between balances obtained with L-Met and Na2SO4 was not significant due to large variation in response to Na2SO4. While addition of D-Met to SB did not result in significantly greater N retention than unsupplemented SB, NA2SO4 addition did cause increased N retention.

Adult↗