Methionine is an organic compound, which is composed ofessential amino acid One, the molecular formula is CfiveHelevenOtwoNS，Optical activity, participationprotein synthesis。
It cannot be generated in the body itself, so it must be obtained from the outside.If methionine is deficient, protein synthesis in the body will be blocked, causing damage to the body.Overoxidation of membrane lipids caused by oxygen free radicals in vivo is the cause of various damages to the body.lipid peroxideWill damage the primary andSecondary lysosomeMembrane, which is used to hydrolyzeacid phosphataseReleased, it can affect the cells andmitochondrial membraneAnd other important organelles. Methionine fights against these damages through various ways.
Chinese name
methionine
Foreign name
Methionine
Alias
Methylthiobutyrate;methionine
chemical formula
CfiveHelevenOtwoNS
molecular weight
one hundred and forty-nine point two one one
CAS login number
59-51-8（D,L-methionine)
EINECS login number
200-432-1（D,L-methionine)
Melting point
270 to 273 ℃（D,L-methionine)
Boiling point
306.9 ℃（D,L-methionine)
Water solubility
soluble
Density
1.340 g/cm³（D,L-methionine)
Appearance
White crystalline powder
Flash point
139.4 ℃
Application
It can be used as a nutrition enhancer of feed and can make up for the balance of amino acids
Solubility: soluble in water, dilute acid and alkali, very slightly soluble in 95% ethanol, insoluble in ether[1]
Molecular structure data
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Molar refractive index: 38.26
Molar volume (cmthree/mol）：123.7
Isotonic specific volume (90.2K): 329.9
Surface tension (dyne/cm): 50.5
Polarization (10-24cmthree）：15.17[1]
Calculate chemical data
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Reference value for drainage parameter calculation (XlogP): None
Number of hydrogen bond donors: 2
Number of hydrogen bond receptors: 4
Number of rotatable chemical bonds: 4
Number of tautomers: 0
Topological molecular polar surface area: 88.6
Number of heavy atoms: 9
Surface charge: 0
Complexity: 97
Number of isotope atoms: 0
Determine the number of atomic structure centers: 0
Number of uncertain atomic structure centers: 1
Determine the number of chemical bond structure centers: 0
Number of uncertain chemical bond structure centers: 0
Number of covalent bond units: 1[1]
purpose
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It is mainly used as a nutritional supplement.The physiological effect of L-methionine is the same as that of L-methionine, but the price is low (L-methionine is made from DL - methionine), so DL methionine is generally used.It is a restricted amino acid in plant foods such as oats, rye, rice, corn, wheat, peanut flour, soybeans, potatoes, spinach, etc.It is added to the above food to improve the amino acid balance.The requirement varies with the intake of cystine.The adult male requirement is 1.1g/d.
The taste of sea urchins is related to methionine, the sweet taste of sea urchins is related to glycine and alanine, the bitter taste is related to valine, and the fresh taste is related to glutamic acid. Therefore, these amino acids can be formulated as flavoring agents.
It is also used for amino acid infusion and comprehensive amino acid preparation.
It can be used as spice according to GB2760-86.
Pharmacopoeia information
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essential information
This product is L-2-amino-4 - (methylthio) butyric acid, calculated as dry product, containing CfiveHelevenNOtwoS shall not be less than 98.5%.
character
This product is white or almost white crystal or crystalline powder, with special odor.
This product is soluble in water, almost insoluble in ethanol, insoluble in ether, and easily soluble in dilute hydrochloric acid or sodium hydroxide solution.
Specific curl
Take this product, weigh it precisely, add 6mol/L hydrochloric acid solution to dissolve it and dilute it quantitatively to make a solution containing about 20mg per 1mL. Determine according to the law (general rule 0621), and the specific rotation is+21.0 ° to+25.0 °.
identify
1. Take 50mg of this product.Add 2mL of water to dissolve, add 1mL of sodium hydroxide test solution, shake up, add 0.6mL of newly prepared sodium nitrite ferricyanide test solution, shake while dropping, place at 40 ° C for 10 minutes, cool in ice bath for 2 minutes, add 2mL of dilute hydrochloric acid, shake up, and the solution turns red.
2. Take appropriate amount of this product and methionine control sample, add water to dissolve and dilute them respectively to prepare test solution and control solution containing about 10mg per 1mL.According to the method under other amino acids, the position and color of the main spot of the test solution should be the same as that of the control solution.
3. The infrared absorption spectrum of this product should be consistent with the control spectrum (spectrum set 1045 figure).
inspect
acidity
Take 0.50g of this product, add 50mL of water to dissolve it, and then determine according to the law (general rule 0631),The pH value should be 5.6-6.1.
Transmittance of solution
Take 0.50g of this product, add 20mL of water to dissolve it, and then measure the transmittance at the wavelength of 430nm according to the ultraviolet visible spectrophotometry (general rule 0401), which shall not be less than 98.0%.
chloride
Take 0.30g of this product and check it according to the law (general rule 0801). Compared with the control solution made of 6.0mL of standard sodium chloride solution, it should not be more concentrated (0.02%).
sulfate
Take 1.0g of this product and check it according to the law (general rule 0802). Compared with the control solution made of 2.0mL of standard potassium sulfate solution, it should not be more concentrated (0.02%).
ammonium salt
Take 0.10g of this product and check it according to the law (general rule 0808). Compared with the control solution made of 2.0mL of standard ammonium chloride solution, it should not be deeper (0.02%).
Other amino acids
Test according to thin layer chromatography (general rule 0502).
Test solution: Take a proper amount of this product, add water to dissolve and dilute it to make a solution containing about 10mg per 1mL.
Reference solution: precisely measure 1mL of the test solution, place it in a 200mL volumetric flask, dilute it with water to the scale, and shake it up.
System suitability solution: Take appropriate amount of methionine reference and serine reference, place them in the same measuring flask, add water to dissolve and dilute them to make a solution containing about 10mg of methionine and 0.1mg of serine per 1mL respectively.
Chromatographic conditions: silica gel G thin layer plate was used, and n-butanol glacial acetic acid water (4:1:5) was used as the developing agent.
Determination method: take 5 µ L of each of the above three solutions, dab them on the same thin plate, develop them, dry them in the air, dry them at 90 ℃ for 10 minutes, spray acetone solution of ninhydrin (0.5 → 100)), heat them at 90 ℃ until spots appear, and inspect them immediately.
System suitability requirements: the reference solution should show a clear spot, and the system suitability solution should show two completely separated spots.
Limit: if the test solution shows impurity spots, there should be no more than one, and its color should not be deeper (0.5%) than the main spot of the control solution.
Loss on drying
Take this product and dry it at 105 ℃ for 3 hours. The weight loss shall not exceed 0.2% (general rule 0831).
Ignition residue
Not more than 0.1% (general rule 0841).
ferric salt
Take 1.0g of this product and check it according to the law (general rule 0807). Compared with the control solution made of 1.5ml of standard iron solution, it should not be deeper (0.0015%).
heavy metal
Take 0.50g of this product, add 23mL of water to dissolve it, add 2mL of acetate buffer (pH 3.5), and check according to the law (General Rule 0821, Method 1). The content of heavy metals should not exceed 10 parts per million.
Arsenite
Take 2.0g of this product, add 23mL of water to dissolve it, add 5mL of hydrochloric acid, and check according to the law (the first method of general rule 0822), which should meet the requirements (0.0001%).
Bacterial endotoxin
Take this product and check it according to the law (general rule 1143). The amount of endotoxin in every 1g methionine should be less than 25EU.(for injection)
Assay
Take about 0.13g of this product, precisely weigh it, add 3mL of anhydrous formic acid to dissolve it, add 50mL of glacial acetic acid, titrate it with perchloric acid titrant (0.1mol/L) according to the potentiometric titration method (General Rule 0701), and correct the titration result with a blank test.Every 1mL perchloric acid titrant (0.1mol/L) is equivalent to 14.92mg CfiveHelevenNOtwoS。
category
Amino acid drugs.
Storage
Sealed storage.
preparation
Methionine Tablets.[2]
metabolism analysis
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Methionine is one of α - amino acids containing sulfur.It is a component of protein. There are a lot of ovalbumin and casein, and the L-type is naturally obtained.It is one of the essential amino acids,L type and D type are effective.Or directly remove methyl mercaptan and ammonia, and indirectly decompose into α - ketoacid through homocysteine.The biosynthesis of methionine is from sulfides such as O-acetylhomoserine, or from the reverse pathway of cysteine to homocysteine (so far only appeared on Streptospora), and then to homocysteine by transferring methyl.
These methyl groups are directly transferred by (1) N-highest positive compound (such as betaine), (2) S-highest positive compound (such as thiobetaine), or newly generated by (3) active C1 unit.Moreover, the active methionine itself is also decomposed into homocysteine, which becomes creatineMethyl donors of N-methylnicotinic acid, choline, methyl histidine, etc.
The active methionine also becomes polyamine through decarboxylation, desulfurization and methyl reaction.Another synthesis route is to generate methionine through the transfer of thiomethyl to α - ketobutyric acid.The sulfur in methionine is stable to the base.Cyanogen bromide can cut off the peptide at the methionine residue, so it is often used in the study of amino acid arrangement.Methionine is one of the eight essential amino acids for human body.It cannot be synthesized in human body and must be supplemented by external sources.Methionine combines with ATP to form S-adenosine in human body.
