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3-Methylornithine is an 
amino acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...
with the formula H2N(CH2)2CH(CH3)CH(NH2)CO2H. This amino acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...
contains two stereogenic center
In stereochemistry, a stereocenter of a molecule is an atom (center), axis or plane that is the focus of stereoisomerism; that is, when having at least three different groups bound to the stereocenter, interchanging any two different groups cr ...
s, but only one stereoisomer
In stereochemistry, stereoisomerism, or spatial isomerism, is a form of isomerism in which molecules have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in ...
(namely (3''R'')-3-methyl-D-ornithine) occurs in nature. It is produced from lysine
Lysine (symbol Lys or K) is an α-amino acid that is a precursor to many proteins. Lysine contains an α-amino group (which is in the protonated form when the lysine is dissolved in water at physiological pH), an α-carboxylic acid group ( ...
by the action of the enzyme methylornithine synthase. The combination of lysine and 3-methylornithine, also mediated enzymatically, produces pyrrolysine
Pyrrolysine (symbol Pyl or O), encoded by the 'amber' stop codon UAG, is a proteinogenic amino acid that is used in some methanogenic archaea and in bacteria. It consists of lysine with a 4-methylpyrroline-5-carboxylate in amide linkage with the ...
, which, for some organisms, is a 22nd genetically coded amino acid.Quitterer, F.; Beck, P.; Bacher, A.; Groll, M., "Structure and Reaction Mechanism of Pyrrolysine Synthase (PylD)", Angew. Chem. Int. Ed. 2013, volume 52, pp. 7033-7037.
See also
*Ornithine
Ornithine is a non-proteinogenic α-amino acid that plays a role in the urea cycle. It is not incorporated into proteins during translation. Ornithine is abnormally accumulated in the body in ornithine transcarbamylase deficiency, a disorder of th ...
References