メチオニン (C11)

Cosmetic ingredients (Methionine) -> CIR (Cosmetic Ingredient Review)

Hair conditioning; Antistatic; Skin conditioning

log Kow = -1.87

-1.87

Minute hexagonal plates from dilute alcohol

Colorless or white, lustrous plates or as white, crystalline powder

Soluble (NTP, 1992)

Soluble in water but the crystals are somewhat water-repellant at first

Soluble in warm dilute alcohol; insoluble in absolute alcohol, ether, petroleum ether, benzene, acetone

Slightly soluble in acetic acid

In water, 56.6 g/L at 25 °C

This chemical does not meet GHS hazard criteria for 97.6% (206 of 211) of all reports.

Not Classified

Aggregated GHS information provided per 211 reports by companies from 7 notifications to the ECHA C&L Inventory.

Chemical: L-Methionine

Regulation (EC) No 1831/2003 (amended)

Methionine is listed on the EPA's Chemical Data Reporting (CDR) system. Manufacturers and importers of Methionine are required to report information about their production and use of this chemical to the EPA under the Toxic Substances Control Act (TSCA). (40 eCFR Part 711)

Status: Active Update: 29-07-2021 https://echa.europa.eu/registration-dossier/-/registered-dossier/19745

Methionine: Does not have an individual approval but may be used under an appropriate group standard

L-Methionine: Does not have an individual approval but may be used under an appropriate group standard

L-Methionine is a food additive permitted for direct addition to food for human consumption, as long as 1) the quantity of the substance added to food does not exceed the amount reasonably required to accomplish its intended physical, nutritive, or other technical effect in food, and 2) any substance intended for use in or on food is of appropriate food grade and is prepared and handled as a food ingredient.

Drug products containing certain active ingredients offered over-the-counter (OTC) for certain uses. A number of active ingredients have been present in OTC drug products for various uses, as described below. However, based on evidence currently available, there are inadequate data to establish general recognition of the safety and effectiveness of these ingredients for the specified uses: methionine is included in weight control drug products.

Methionine used as a nutrient and/or dietary supplement in animal drugs, feeds, and related products is generally recognized as safe when used in accordance with good manufacturing or feeding practice.

NAS, Food and Nutrition Board, Institute of Medicine; Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). National Academy Press, Washington, D.C. (2009).[Available from, as of March 10, 2010: http://www.nap.edu/catalog/10490.html]

Chemical: DL-Methionine

Chemical: L-Methionine

EYES: First check the victim for contact lenses and remove if present. Flush victim's eyes with water or normal saline solution for 20 to 30 minutes while simultaneously calling a hospital or poison control center. Do not put any ointments, oils, or medication in the victim's eyes without specific instructions from a physician. IMMEDIATELY transport the victim after flushing eyes to a hospital even if no symptoms (such as redness or irritation) develop.

SMALL SPILLS AND LEAKAGE: If you spill this chemical, you should dampen the solid spill material with water, then transfer the dampened material to a suitable container. Use absorbent paper dampened with water to pick up any remaining material. Seal your contaminated clothing and the absorbent paper in a vapor-tight plastic bag for eventual disposal. Wash all contaminated surfaces with a soap and water solution. Do not reenter the contaminated area until the Safety Officer (or other responsible person) has verified that the area has been properly cleaned.

SRP: Expired or waste pharmaceuticals shall carefully take into consideration applicable DEA, EPA, and FDA regulations. It is not appropriate to dispose by flushing the pharmaceutical down the toilet or discarding to trash. If possible return the pharmaceutical to the manufacturer for proper disposal being careful to properly label and securely package the material. Alternatively, the waste pharmaceutical shall be labeled, securely packaged and transported by a state licensed medical waste contractor to dispose by burial in a licensed hazardous or toxic waste landfill or incinerator.

SRP: At the time of review, regulatory criteria for small quantity disposal are subject to significant revision, however, household quantities of waste pharmaceuticals may be managed as follows: Mix with wet cat litter or coffee grounds, double bag in plastic, discard in trash.

SRP: Criteria for land treatment or burial (sanitary landfill) disposal practices are subject to significant revision. Prior to implementing land disposal of waste residue (including waste sludge), consult with environmental regulatory agencies for guidance on acceptable disposal practices.

RECOMMENDED RESPIRATOR: Where the neat test chemical is weighed and diluted, wear a NIOSH-approved half face respirator equipped with an organic vapor/acid gas cartridge (specific for organic vapors, HCl, acid gas and SO2) with a dust/mist filter. (NTP, 1992)

The adverse effects of methionine are alleviated by supplements of glycine or serine ... Vit B6 deficiency reduces the tolerance of the rat for methionine.

Pretreatment of young male rats with excess retinol (800 IU/g diet for 10 days) partially counteracted the adverse effects caused by a high methionine intake.

Methionine provided in the drinking water of pregnant rats injected with sodium valproate reduced the frequency of resorptions but did not improve embryo growth. Rats drinking methionine supplemented water had approx twice the level of serum free methionine and consumed only one half the volume of water as controls. Using whole rat embryo cultures, the simultaneous addition of methionine and sodium valproate to the medium provided no protection from the teratogenic effects of sodium valproate ... Protection from the teratogenic effects of sodium valproate was afforded by methionine and was particularly striking when embryos for culture were taken from pregnant rats that had been consuming methionine.

This study showed that short-term vitamin administration /(folic acid, vitamins B6 and B12)/ effectively reduced post-methionine load homocysteine levels and thereby ameliorated endothelium-dependent flow-mediated vasodilation in 16 healthy adults. Post-methionine load homocysteine levels decreased from 22.7+/-3.8 to 17.0+/-2.1 micromol/L (p <0.001), and flow-mediated vasodilation after methionine load increased from 8.6+/-3.6% to 13.8+/-2.9% (p <0.001) after vitamin administration.

For more Interactions (Complete) data for (L)-Methionine (18 total), please visit the HSDB record page.

Chronically high levels of methionine are associated with at least 7 inborn errors of metabolism including: Cystathionine Beta-Synthase Deficiency, Glycine N-methyltransferase Deficiency, Homocystinuria-megaloblastic anemia due to defect in cobalamin metabolism, Methionine Adenosyltransferase Deficiency, Methylenetetrahydrofolate reductase deficiency and S-Adenosylhomocysteine (SAH) Hydrolase Deficiency.

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 8(SRC), determined from a log Kow of -1.87(2) and a regression-derived equation(3), indicates that (L)-methionine is expected to have very high mobility in soil(SRC). The pKa values of (L)-methionine are 2.28 and 9.21(4), indicate that this compound will exist as a zwitterion which may affect its adsorption to soils and sediments(SRC). Volatilization from moist soil is not expected because ions do not volatilize(SRC). (L)-Methionine is not expected to volatilize from dry soil surfaces(SRC) based upon an estimated vapor pressure of 8.1X10-8 mm Hg at 25 °C(SRC), determined from a fragment constant method(5). Using a laboratory activated sludge system, (L)-methionine exhibited an 80% theoretical BOD reduction in 16 days, producing 3-mercaptopropionate, methanethiol and dimethylsulfide(6); this suggests that biodegradation may be an important environmental fate process in soil(SRC).

AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 8(SRC), determined from a log Kow of -1.87(2) and a regression-derived equation(3), indicates that (L)-methionine is not expected to adsorb to suspended solids and sediment(SRC). The pKa values of 2.28 and 9.21(4) indicates (L)-methionine will exist as a zwitterion at pH values of 5 to 9 and therefore volatilization from water surfaces is not expected to be an important fate process(5). According to a classification scheme(6), an estimated BCF of 3(SRC), from its log Kow(2) and a regression-derived equation(7), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Using a laboratory activated sludge system, (L)-methionine exhibited an 80% theoretical BOD reduction in 16 days, producing 3-mercaptopropionate, methanethiol and dimethylsulfide(8); this suggests that biodegradation may be an important environmental fate process in water(SRC).

AQUATIC FATE: (L)-Methionine has been shown to degrade in sunlit natural water through a photo-sensitized oxidation involving singlet oxygen(1,2); assuming that the top meter of sunlit natural water has a singlet oxygen concn of 4X10-14 M, the photooxidation half-life for the reaction (L)-methionine with singlet oxygen has been estimated to be about 200 hr at pH 6-11(1); the near-surface photooxidation rate (via singlet oxygen) of (L)-methionine in Okefenokee Swamp water from Georgia is predicted to be about 3 hr(2). Bioconcentration and volatilization are not expected to important fate processes because of its high water solubility(SRC).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), (L)-methionine, which has an estimated vapor pressure of 8.1X10-8 mm Hg at 25 °C(SRC), determined from a fragment constant method(2), will exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase (L)-methionine is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 7.5 hours(SRC), calculated from its rate constant of 5.1X10-11 cu cm/molecule-sec at 25 °C(SRC) that was derived using a structure estimation method(3). (L)-Methionine does not contain chromophores that absorb at wavelengths >290 nm(4) and therefore is not expected to be susceptible to direct photolysis by sunlight(SRC).

The average methionine content of some foodstuffs (in mg/100g) has been reported as follows: maize, grain: 182; rice, husked: 183; wheat, whole grain: 196; potato: 26; bean (Phaselous vulgaris): 234; soybean, milk: 50; soy protein, isolate: 1008; tomato: 7; apple: 3; orange: 12; beef, veal, edible flesh: 478; fish: 220; cheese: 530; egg, whole: 416(1).

Safe in the present practices of use and concentration. Ingredient, concentration, and use information are available in documents discoverable at https://cir-reports.cir-safety.org

The mechanism of the possible anti-hepatotoxic activity of L-methionine is not entirely clear. It is thought that metabolism of high doses of acetaminophen in the liver lead to decreased levels of hepatic glutathione and increased oxidative stress. L-methionine is a precursor to L-cysteine. L-cysteine itself may have antioxidant activity. L-cysteine is also a precursor to the antioxidant glutathione. Antioxidant activity of L-methionine and metabolites of L-methionine appear to account for its possible anti-hepatotoxic activity. Recent research suggests that methionine itself has free-radical scavenging activity by virtue of its sulfur, as well as its chelating ability.

The Koc of (L)-methionine is estimated as 8(SRC), using a log Kow of -1.87(1) and a regression-derived equation(2). According to a classification scheme(3), this estimated Koc value suggests that (L)-methionine is expected to have very mobility in soil. The pKa values of (L)-methionine are 2.28 and 9.21(4), indicate that this compound will exist as a zwitterion which may affect its adsorption to soils and sediments(SRC). One study found that (L)-methionine was one of many amino acids that sorbed to carbonate sediments in seawater(5); a positive correlation between surface area (of the sediment) and the amount of sorbed amino acids indicated that sorption from solution (partitioning from the water column to sediment) was a likely mechanism(5).

L-Methionine is a food additive permitted for direct addition to food for human consumption, as long as 1) the quantity of the substance added to food does not exceed the amount reasonably required to accomplish its intended physical, nutritive, or other technical effect in food, and 2) any substance intended for use in or on food is of appropriate food grade and is prepared and handled as a food ingredient.

Drug products containing certain active ingredients offered over-the-counter (OTC) for certain uses. A number of active ingredients have been present in OTC drug products for various uses, as described below. However, based on evidence currently available, there are inadequate data to establish general recognition of the safety and effectiveness of these ingredients for the specified uses: methionine is included in weight control drug products.

Methionine used as a nutrient and/or dietary supplement in animal drugs, feeds, and related products is generally recognized as safe when used in accordance with good manufacturing or feeding practice.

V - Various

QG - Genito urinary system and sex hormones

QA - Alimentary tract and metabolism

QV - Various

Plays an important role in biological methylation. Both l- and d-forms are effective in rat and man. D-form undergoes deamination, and the keto compound is then transaminated with the resultant inversion of the natural l-form.

Methionine restriction (MR) limits age-related adiposity in Fischer 344 (F344) rats. To assess the mechanism of adiposity resistance, the effect of MR on adipose tissue (AT) 11beta-hydroxysteroid dehydrogenase-1 (11beta-HSD1) was examined. MR induced 11beta-HSD1 activity in all ATs, correlating with increased tissue corticosterone. However, an inverse relationship between 11beta-HSD1 activity and adipocyte size was observed. Because dietary restriction controls lipogenic and lipolytic rates, MR's effects on lipogenic and lipolytic enzymes were evaluated. MR increased adipose triglyceride lipase and acetyl-coenzyme A carboxylase (ACC) protein levels but induced ACC phosphorylation at serine residues that render the enzyme inactive, suggesting alterations of basal lipolysis and lipogenesis. In contrast, no changes in basal or phosphorylated hormone-sensitive lipase levels were observed. ACC-phosphorylated sites were specific for AMP-activated protein kinase (AMPK); therefore, AMPK activation was evaluated. Significant differences in AMPKalpha protein, phosphorylation, and activity levels were observed only in retroperitoneal fat from MR rats. No differences in protein kinase A phosphorylation and intracellular cAMP levels were detected. In vitro studies revealed increased lipid degradation and a trend toward increased lipid synthesis, suggesting the presence of a futile cycle. In conclusion, MR disrupts the lipogenic/lipolytic balance, contributing importantly to adiposity resistance in F344 rats.

The methionine choline-deficient (MCD) diet results in liver injury similar to human nonalcoholic steatohepatitis (NASH). The aims of this study were to define mechanisms of MCD-induced steatosis in insulin-resistant db/db and insulin-sensitive db/m mice. MCD-fed db/db mice developed more hepatic steatosis and retained more insulin resistance than MCD-fed db/m mice. Both subcutaneous and gonadal fat were reduced by MCD feeding: gonadal fat decreased by 23% in db/db mice and by 90% in db/m mice. Weight loss was attenuated in the db/db mice, being only 13% compared with 35% in MCD-fed db/db and db/m mice, respectively. Both strains had upregulation of hepatic fatty acid transport proteins as well as increased hepatic uptake of [14C]oleic acid: 3-fold in db/m mice (P < 0.001) and 2-fold in db/db mice (P < 0.01) after 4 weeks of MCD feeding. In both murine strains, the MCD diet reduced triglyceride secretion and downregulated genes involved in triglyceride synthesis. Therefore, increased fatty acid uptake and decreased VLDL secretion represent two important mechanisms by which the MCD diet promotes intrahepatic lipid accumulation in this model...

In women whose average daily intake of methionine was above the lowest quartile of intake (greater than 1.34 g/day), a 30 to 40% reduction in neural tube defect-affected pregnancies was observed. These reductions were observed for both anencephaly and spina bifida.

For more Bionecessity (Complete) data for (L)-Methionine (20 total), please visit the HSDB record page.

L-Methionine is a principle supplier of sulfur which prevents disorders of the hair, skin and nails; helps lower cholesterol levels by increasing the liver's production of lecithin; reduces liver fat and protects the kidneys; a natural chelating agent for heavy metals; regulates the formation of ammonia and creates ammonia-free urine which reduces bladder irritation; influences hair follicles and promotes hair growth. L-methionine may protect against the toxic effects of hepatotoxins, such as acetaminophen. Methionine may have antioxidant activity.

The mechanism of the possible anti-hepatotoxic activity of L-methionine is not entirely clear. It is thought that metabolism of high doses of acetaminophen in the liver lead to decreased levels of hepatic glutathione and increased oxidative stress. L-methionine is a precursor to L-cysteine. L-cysteine itself may have antioxidant activity. L-cysteine is also a precursor to the antioxidant glutathione. Antioxidant activity of L-methionine and metabolites of L-methionine appear to account for its possible anti-hepatotoxic activity. Recent research suggests that methionine itself has free-radical scavenging activity by virtue of its sulfur, as well as its chelating ability.

Amino acids are selected for protein synthesis by binding with transfer RNA (tRNA) in the cell cytoplasm. The information on the amino acid sequence of each individual protein is contained in the sequence of nucleotides in the messenger RNA (mRNA) molecules, which are synthesized in the nucleus from regions of DNA by the process of transcription. The mRNA molecules then interact with various tRNA molecules attached to specific amino acids in the cytoplasm to synthesize the specific protein by linking together individual amino acids; this process, known as translation, is regulated by amino acids (e.g., leucine), and hormones. Which specific proteins are expressed in any particular cell and the relative rates at which the different cellular proteins are synthesized, are determined by the relative abundances of the different mRNAs and the availability of specific tRNA-amino acid combinations, and hence by the rate of transcription and the stability of the messages. From a nutritional and metabolic point of view, it is important to recognize that protein synthesis is a continuing process that takes place in most cells of the body. In a steady state, when neither net growth nor protein loss is occurring, protein synthesis is balanced by an equal amount of protein degradation. The major consequence of inadequate protein intakes, or diets low or lacking in specific indispensable amino acids relative to other amino acids (often termed limiting amino acids), is a shift in this balance so that rates of synthesis of some body proteins decrease while protein degradation continues, thus providing an endogenous source of those amino acids most in need. /Protein synthesis/

The mechanism of intracellular protein degradation, by which protein is hydrolyzed to free amino acids, is more complex and is not as well characterized at the mechanistic level as that of synthesis. A wide variety of different enzymes that are capable of splitting peptide bonds are present in cells. However, the bulk of cellular proteolysis seems to be shared between two multienzyme systems: the lysosomal and proteasomal systems. The lysosome is a membrane-enclosed vesicle inside the cell that contains a variety of proteolytic enzymes and operates mostly at acid pH. Volumes of the cytoplasm are engulfed (autophagy) and are then subjected to the action of the protease enzymes at high concentration. This system is thought to be relatively unselective in most cases, although it can also degrade specific intracellular proteins. The system is highly regulated by hormones such as insulin and glucocorticoids, and by amino acids. The second system is the ATP-dependent ubiquitin-proteasome system, which is present in the cytoplasm. The first step is to join molecules of ubiquitin, a basic 76-amino acid peptide, to lysine residues in the target protein. Several enzymes are involved in this process, which selectively targets proteins for degradation by a second component, the proteasome. /Protein degradation/

Methionine dependence, the inability of cells to grow when the amino acid methionine is replaced in culture medium by its metabolic precursor homocysteine, is characteristic of many cancer cell lines and some tumors in situ. Most cell lines proliferate normally under these conditions. The methionine dependent tumorigenic human melanoma cell line MeWo-LC1 was derived from the methionine independent non-tumorigenic line, MeWo. MeWo-LC1 has a cellular phenotype identical to that of cells from patients with the cblC inborn error of cobalamin metabolism, with decreased synthesis of cobalamin coenzymes and decreased activity of the cobalamin-dependent enzymes methionine synthase and methylmalonylCoA mutase. Inability of cblC cells to complement the defect in MeWo-LC1 suggested that it was caused by decreased activity of the MMACHC gene. However, no potentially disease causing mutations were detected in the coding sequence of MMACHC in MeWo-LC1. No MMACHC expression was detected in MeWo-LC1 by quantitative or non-quantitative PCR. There was virtually complete methylation of a CpG island at the 5'-end of the MMACHC gene in MeWo-LC1, consistent with inactivation of the gene by methylation. The CpG island was partially methylated (30-45%) in MeWo and only lightly methylated (2-11%) in control fibroblasts. Infection of MeWo-LC1 with wild type MMACHC resulted in correction of the defect in cobalamin metabolism and restoration of the ability of cells to grow in medium containing homocysteine. /It was concluded/ that epigenetic inactivation of the MMACHC gene is responsible for methionine dependence in MeWo-LC1.

Hepatic

Product of oxidative deamination or transamination--alpha-keto-gamma-methiolbutyric acid. /From table/

... Oxidation of methionine (S-methyl-l-cysteine and sarcosine) methyl group in vivo proceeds primarily by way of free formate, and that conversion to formate is probably not catalysed by tetrahydrofolic acid.

... Methionine ... is catabolized to a large extent independently of initial activation to S-adenosyl-l-methionine. The system for catabolism ... appears analogous to one that catalyses oxidation of S-methyl-l-cysteine methyl group ... The methyl group of methionine ... /has been/ shown ... to yield formate in vitro and in vivo.

Infants more rapidly metabolized methionine than adults.

For more Metabolism/Metabolites (Complete) data for (L)-Methionine (7 total), please visit the HSDB record page.

Absorbed from the lumen of the small intestine into the enterocytes by an active transport process.

... Rats were fed diets containing [(14)C-methyl]l-methionine ... with 6% of sodium formate, and conversion of (14)C into [(14)C]formate was measured in urine and exhaled air (as (14)CO2) ... Total oxidation of [(14)C-methyl] into CO2, amounted to 60-87% for methionine ...

Although the free amino acids dissolved in the body fluids are only a very small proportion of the body's total mass of amino acids, they are very important for the nutritional and metabolic control of the body's proteins. ... Although the plasma compartment is most easily sampled, the concentration of most amino acids is higher in tissue intracellular pools. Typically, large neutral amino acids, such as leucine and phenylalanine, are essentially in equilibrium with the plasma. Others, notably glutamine, glutamic acid, and glycine, are 10- to 50-fold more concentrated in the intracellular pool. Dietary variations or pathological conditions can result in substantial changes in the concentrations of the individual free amino acids in both the plasma and tissue pools. /Amino acids/

After ingestion, proteins are denatured by the acid in the stomach, where they are also cleaved into smaller peptides by the enzyme pepsin, which is activated by the increase in stomach acidity that occurs on feeding. The proteins and peptides then pass into the small intestine, where the peptide bonds are hydrolyzed by a variety of enzymes. These bond-specific enzymes originate in the pancreas and include trypsin, chymotrypsins, elastase, and carboxypeptidases. The resultant mixture of free amino acids and small peptides is then transported into the mucosal cells by a number of carrier systems for specific amino acids and for di- and tri-peptides, each specific for a limited range of peptide substrates. After intracellular hydrolysis of the absorbed peptides, the free amino acids are then secreted into the portal blood by other specific carrier systems in the mucosal cell or are further metabolized within the cell itself. Absorbed amino acids pass into the liver, where a portion of the amino acids are taken up and used; the remainder pass through into the systemic circulation and are utilized by the peripheral tissues. /Amino acids/

Protein secretion into the intestine continues even under conditions of protein-free feeding, and fecal nitrogen losses (ie, nitrogen lost as bacteria in the feces) may account for 25% of the obligatory loss of nitrogen. Under this dietary circumstance, the amino acids secreted into the intestine as components of proteolytic enzymes and from sloughed mucosal cells are the only sources of amino acids for the maintenance of the intestinal bacterial biomass. ... Other routes of loss of intact amino acids are via the urine and through skin and hair loss. These losses are small by comparison with those described above, but nonetheless may have a significant impact on estimates of requirements, especially in disease states. /Amino acids/

For more Absorption, Distribution and Excretion (Complete) data for (L)-Methionine (11 total), please visit the HSDB record page.

CIR ingredient: Methionine

An essential amino acid; Used therapeutically as an antidote for acetaminophen poisoning and a urinary acidifier; [Merck Index] Chelating agent for heavy metals; [ChemIDplus] Used as a flavoring agent and nutritional supplement for foods; [FDA] Used in pharmaceuticals, as a feed additive, for vegetable oil enrichment, and as single cell protein; [NTP] Permitted for use as an inert ingredient in non-food pesticide products; [EPA]

Farming (Feed Additives) [Category: Industry]

Feed additive; vegetable oil enrichment; single-cell protein /DL-Methionine/

Nutrient

BIOLOGICAL ACTIVITIES: Anticataract; antidote (acteaminophen, paracetamol); antieczemic; antihepatotic; antioxidant; antiparkinsonian; cancer-preventive; emetic; essential; glutathionigenic; heptoprotective; lioptropic; urine-acidifier, urine-deodorant

2021: 246,400 lb

(1992) No data

World market for L-methionine in 1982: 150 tons; World market for DL-methionine in 1982: 110,000 tons

Production volumes for non-confidential chemicals reported under the Inventory Update Rule. [Table#4914]

The production method of choice for L-methionine is still the enzymatic resolution of racemic N-acetyl-methionine using acylase from Aspergillus oryzae. The production is carried out in a continuously operated fixed-bed or enzyme membrane reactor. Alternatively, L-methionine may be produced by microbial conversion of the corresponding 5-substituted hydantoin. With growing cells of Pseudomonas sp. strain NS671, D,L-5-(2-methylthioethyl)hydantoin was converted to L-methionine; a final concentration of 34 g/L and a molar yield of 93% have been obtained.

The most economic way for production of D,L-methionine is the chemical process based on acrolein, methyl mercaptan, hydrogen cyanide, and ammonium carbonate. beta-Methylthiopropionaldehyde, formed by addition of methyl mercaptan to acrolein, is the intermediate that reacts with hydrogen cyanide to give alpha-hydroxy-gamma-methylthiobutyronitrile. Treatment with ammonium carbonate leads to 5-(beta-methylthioethyl)hydantoin that is saponified by potassium carbonate giving D,L-methionine in up to 95% yield, calculated on acrolein. /D,L-Methionine/

NF, feed 98%

USP and FCC grades; 99% feed grade

Racemate mixture of D- and L- methionine

EPA Safer Chemical Functional Use Classes -> Enzymes and Enzyme Stabilizers

Safer Chemical Classes -> Green circle - The chemical has been verified to be of low concern

EPA Safer Chemical Functional Use Classes -> Skin Conditioning Agents

Safer Chemical Classes -> Green half-circle - The chemical is expected to be of low concern

Cosmetics -> Hair conditioning; Antistatic; Skin conditioning

Not Known or Reasonably Ascertainable

Methionine: ACTIVE

L-Methionine: ACTIVE

... Available as d,l-methionine and as calcium salt of hydroxy analog of methionine. These products are used ... in animal feeds ... Relative biological value of these compared to l-methionine ... evidence suggests equivalency on mole basis both in rats and man.

The D-form of methionine is as equally nutritive as the L-form, so that DL-methionine which is inexpensively produced by the chemical synthesis is primarily used as a feed supplement

The amino acids that are incorporated into mammalian protein are alpha-amino acids, with the exception of proline, which is an alpha-imino acid. This means that they have a carboxyl group, an amino nitrogen group, and a side chain attached to a central alpha-carbon. Functional differences among the amino acids lie in the structure of their side chains. In addition to differences in size, these side groups carry different charges at physiological pH (e.g., nonpolar, uncharged but polar, negatively charged, positively charged); some groups are hydrophobic (e.g., branched chain and aromatic amino acids) and some hydrophilic (most others). These side chains have an important bearing on the ways in which the higher orders of protein structure are stabilized and are intimate parts of many other aspects of protein function.