methionine

(mĕthī`ənēn), organic compound, one of the 20 amino acidsamino acid
, any one of a class of simple organic compounds containing carbon, hydrogen, oxygen, nitrogen, and in certain cases sulfur. These compounds are the building blocks of proteins.
..... Click the link for more information. commonly found in animal proteins. Only the L-stereoisomer appears in mammalian protein. It is one of the several essential amino acids needed in the diet; the human body cannot synthesize it from simpler metabolites. It is an important source of dietary sulfur. Methionine reacts with adenosine triphosphateadenosine triphosphate
(ATP) , organic compound composed of adenine, the sugar ribose, and three phosphate groups. ATP serves as the major energy source within the cell to drive a number of biological processes such as photosynthesis, muscle contraction, and the synthesis of
..... Click the link for more information. to form S-adenosyl methionine, a potent donor of methyl groups (composed of one carbon and three hydrogen atoms); S-adenosyl methionine is the principal methyl donor in the body and contributes to the synthesis of many important substances, including epinephrineepinephrine
, hormone important to the body's metabolism, also known as adrenaline. Epinephrine, a catecholamine, together with norepinephrine, is secreted principally by the medulla of the adrenal gland.
..... Click the link for more information. and choline (see acetylcholineacetylcholine
, a small organic molecule liberated at nerve endings as a neurotransmitter. It is particularly important in the stimulation of muscle tissue. The transmission of an impulse to the end of the nerve causes it to release neurotransmitter molecules onto the surface of
..... Click the link for more information. ; vitaminvitamin,
group of organic substances that are required in the diet of humans and animals for normal growth, maintenance of life, and normal reproduction. Vitamins act as catalysts; very often either the vitamins themselves are coenzymes, or they form integral parts of coenzymes.
..... Click the link for more information. ). Since methionine is the only essential amino acid not present in significant amounts of soybeans, it is produced commercially as an additive for soybean meal. Methionine was isolated from casein (milk protein) in 1922, and its structure was proved by laboratory synthesis in 1928.

Methionine

α-amino-γ-methylmercaptobutyric acid, CH₃SCH₂CH₂CH(NH₂)COOH; a sulfur-bearing monocarboxylic amino acid. Methionine exists in D- and L- forms and in a racemic DL- form. L-methionine is a component of most vegetable and animal proteins. It was isolated in 1922 from the products of the acid hydrolysis of casein.

In mammals and man, methionine is a donor of methylene groups in the body. In its S-adenosyl form (active methionine, a product of the reaction of methionine with ATP in the presence of Mg²+ ions), methionine participates in enzymic transmethylation processes, which lead to the formation of choline, adrenalin, and other biologically important substances. It also serves as a source of sulfur in the biosynthesis of cysteine.

The initial substance in the biosynthesis of methionine is aspartic acid, which undergoes a series of conversions to methionine’s immediate precursor, homocysteine. This series of conversions can occur only in certain microorganisms and plants. Homocysteine can also undergo methylation in mammals, enzymically or by direct transfer of a methyl group from donor molecules.

Methionine is an essential amino acid, the daily adult human requirement for which is 2.5–3 g. Methionine deficiency in the diet of animals and man leads to impairment of protein biosyn-thesis, retardation of growth and development, and severe functional disorders. Synthetic methionine, produced industrially from propylene, is used medicinally and to enrich fodders and food. The D- and L- forms of methionine are of equal value, since they are capable of interconversion in the body.

WORKS

Maister, A. Biokhimiia aminokislot. Moscow, 1961. (Translated from English.)

E. N. SAFONOVA

methionine

[mə′thī·ə‚nēn] (biochemistry) C₅H₁₁O₂NS An essential amino acid; furnishes both labile methyl groups and sulfur necessary for normal metabolism.

methionine

[mĕ-thi´o-nēn] a sulfur-containing amino acid, one of the essential amino acids, furnishing both methyl groups and sulfur necessary for metabolism.

me·thi·o·nine (Met, M),

(me-thī'ō-nēn), The l-isomer is a nutritionally essential amino acid and the most important natural source of "active methyl" groups in the body, hence usually involved in methylations in vivo; the dl-form is used as an adjunct in the treatment of liver diseases.

methionine

(mə-thī′ə-nēn′)n. A sulfur-containing essential amino acid, C₅H₁₁NO₂S, obtained from various proteins or prepared synthetically and used as a dietary supplement and in pharmaceuticals.

me·thi·o·nine

(me-thī'ō-nēn) A nutritionally essential amino acid and the most important natural source of "active methyl" groups in the body, hence usually involved in methylations in vivo.

methionine

An antidote used to treat paracetamol poisoning from overdose. A drug used in combination with paracetamol to protect the liver against the serious damage that is caused by deliberate overdosage. A brand name of the combination is Paradote.

Fig. 221 Methionine . Molecular structure.

methionine (M, Met)

one of 20 AMINO ACIDS common in proteins. It has an ‘R’ group with a nonpolar structure and is relatively insoluble in water. See Fig. 221 . The ISOELECTRIC POINT of methionine is 5.7.

me·thi·o·nine

(M) (me-thī'ō-nēn) The l-isomer is a nutritionally essential amino acid and the most important natural source of "active methyl" groups in the body.

methionine

me·thi·o·nine

methionine

me•thi•o•nine

me·thi·o·nine

methionine

methionine

Methionine

WORKS

methionine

methionine

methionine

me·thi·o·nine (Met, M),

methionine

me·thi·o·nine

methionine

methionine (M, Met)

me·thi·o·nine

methionine

Words related to methionine

noun a crystalline amino acid containing sulfur

Related Words