Methionine biochemical structure

Kauss, H., Swanson, A.L. Hassid, W.Z. (1967) Biosynthesis of the Methyl Ester Groups of Pectin by Transmethylation from S-Adenosyl-L-methionine , Biochemical and Biophysical Research Communications, 26, 234-40 Kawasaki, T. Ashwell, G. (1976) Carbohydrate Structure of Glycopeptides Isolated from Hepatic Membrane-binding Protein Specific for Asialoglycoproteins , Journal of Biological Chemistry, 251, 5292-9... 

I. Inorganic sulfur compounds containing another (usually more electropositive) element. When the other element is an alkali or alkaline earth, the sulfide is ionic in character. Metal sulfides often have unusual stoichiometries. Examples of sulfides include H2S, Na2S, FeS, and HgS. 2. Organic sulfides are also referred to as thioethers and have the general structure R—S—R. Biochemical examples of sulfides include methionine, cystathionine, and djenkolic acid. If the two R groups are identical, the substance can be referred to as a symmetrical sulfide (biological examples of which are lanthionine and homo-lanthionine). 

So far only a few dozen organofluorine compounds have been isolated from living organisms, for example fluoroacetic acid, 4-fluorothreonine and rw-fluoro-oleic acid [244-246], The reason that nature has not invested in fluorine chemistry could be a combination of low availability of water-dissolved fluoride in the environment due to its tendency to form insoluble fluoride salts, and the low reactivity of water-solvated fluoride ion. However, in 2002, O Hagan and collaborators [247] published the discovery of a biochemical fluorination reaction in a bacterial protein extract from Streptomyces cattleya converting S-adenosyl-L-methionine (SAM) to 5 -fluoro-5 deoxyadenosine (5 -FDA). The same protein extract contained also the necessary enzymatic activity to convert 5 -FDA into fluoroacetic acid. In 2004, the same authors published the crystal structure of the enzyme and demonstrated a nucleophilic mechanism of fluorination [248,249]. 

Dissection of the chemical structure of jamaicamides A-C led to the speculation that these metabolites derive from a mixture of polyketides (nine acetate units), amino acids (t-Ala and p-Ala), and the S-methyl group of methionine. To map out the biosynthetic subunits of these molecules, isotopically labeled precursors were supplied to I. majuscula JHB, and the labeling patterns discerned by NMR spectroscopy (Figure 6.12). From these experiments, insights were gained into the biochemical transformations that produce the jamaicamides, especially the mechanism of formation of the vinyl chloride group [157]. 

The keratinization of epithelial structures has long been recognized as a feature of vitamin A deficiency, but the biochemical and ultrastructural details of this lesion are poorly understood. Keratinization implies accumulation of keratin, an insoluble protein rich in cystine sulfhydryl linkages. The incorporation of methionine- S into the skin of vitamin A deficient rats is markedly increased (173), and the incorporation of inorganic S04, presumably into mucopolysaccharides, is decreased. There is also evidence for an increased conversion of cystine into inorganic sulfate (174), and the total cystine content of skin is depressed (175). 

Kagan RM, Clarke S. Widespread occurence of three sequence morift in divers S-adenosyl-methionine dependent methyltransferases suggests a common structure for these enzymes. Arch Biochem Biophy 1994 310 417 27. 

We may divide the sulfur compounds into primary and conjugated, the primary compounds forming a part of more complex chemical structures in the latter. The major primary sulfur compounds that have an established role in the normal biochemical processes of the vertebrate range in variety from the simple inorganic compounds, sulfate, thiosulfate, and thiocyanate, to the amino acids, cysteine, cystine, methionine,... 

Inoue, H., Inagaki, K., Sugimoto, M., Esaki, N., Soda, K., and Tanaka, H., 1995, Structural analysis of the L-methionine y-lyase gene from Pseudomonas putida. J. Biochem. 117 1120-1125. 

Adenosyl-L-methionine (SAM) was discovered in 1952 by Cantoni (1952), and its lUPAC name was designated as (25)-2-Amino-4-[[(25,35,4/ ,5/ )-5-(6-aminopurin-9-yl)-3,4-dihydroxyoxolan-2-yl]methyl-methylsulfonio] butanoate. The molecular structure in Fig. 16.1 shows that SAM possesses a sulfonium ion with a high group transfer potential. Thus each of the attached carbons is activated toward nucleophilic attack. SAM is involved in three types of important biochemical reactions within living cells, including transmethylation, transsulfu-ration, and aminopropylation. 

Odani, S., Odani, S., 1998. Isolation and primary structure of a methionine- and cystine-rich seed protein of Cannabis sativa. Biosci. Biotechnol. Biochem. 62, 650-654. 

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