Biosynthesis from methionine

Homocysteine. A sulfur-containing amino acid, a homologue of cysteine, produced by the demethylation of methionine, and an intermediate in the biosynthesis from methionine via cystathionine. 

One of the major methylating agents in biological systems is 5-adenosylmethionine. Its biosynthesis, from methionine and ATP, is catalysed by 5-adenosyl synthase. In the first... 

The ansa-chain of the ansamycins streptovaricins (4), rifamycins (263), geldanamycin (4), and herbimycin (32) has been shown to be polyketide in origin, being made up of propionate and acetate units with the 0-methyl groups coming from methionine. The remaining aromatic C N portion of the ansamacroHdes is derived from 3-amino-5-hydroxybenzoic acid (264—266) which is formed via shikimate precursors. Based on the precursors of the rifamycins and streptovaricins isolated from mutant bacteria strains, a detailed scheme for the biosynthesis of most of the ansamacroHdes has been proposed (95,263). 

Adenosine triphosphate, coupled reactions and. 1128-1129 function of, 157, 1127-1128 reaction with glucose, 1129 structure of, 157, 1044 S-Adenosylmethionine, from methionine, 669 function of, 382-383 stereochemistry of, 315 structure of, 1045 Adipic acid, structure of, 753 ADP, sec Adenosine diphosphate Adrenaline, biosynthesis of, 382-383 molecular model of, 323 slructure of, 24... 

Leete, E. Biosynthesis of azetidine-2 carboxylic acid from methionine in Nicotiana tahacum. Phytochemistry... 

FIGURE 22-14 Biosynthesis of cysteine from homocysteine and serine in mammals. The homocysteine is formed from methionine, as described in the text. 

Biosynthesis. The terminal C methyl of the propyl side chain, the S-methyl. and the /V methyl groups are derived from methionine, trans-4-Propyl-L-proline was shown to accumulate when Strepromyces lincolnensis is grown in media deficient in sulfur, and the addition of T. tyrosine or L-dihydroxyphenylalaiiine (DOPA) was shown to stimulate this production. 

Information on the biosynthesis of the phenolic glycolipids is very limited.220 The carbon atoms in the methyl-branched structures in mycocerosic acids are derived from propanoate.221-222 So also are those in phthiocerol.223 224 The aromatic ring can be derived from tyrosine.224 The methoxyl residue in phenolphthiocerol presumably comes from methionine, by analogy with the known source in the related lipid phthiocerol.225 226 Rainwater and Kolatukuddy226 demonstrated two steps in the biosynthesis of mycocerosic acids, and isolated the enzymes involved, but the biosynthetic steps leading to phenolphthiocerol itself are not known. 

The first studies on the biosynthesis of ephedrine in Ephedra distachya suggested that phenylalanine was incorporated via a C6—C2—N unit (339). When this was reinvestigated more recently, it was found that while C-3 and the aromatic ring of phenylalanine are incorporated, C-2 is not (341, 342). Specific incorporation of C-3 of phenylalanine into norpseudoephedrine in Catha edulis had also been reported (343). Further incorporation experiments showed that [carhaxy/-l4C]benzoate, [7-l4-C]benzaldehyde, and [3-l4C]cinnamic acid are all efficiently incorporated into the a carbon of ephedrine, and the participation of a C6—C, intermediate rather than a C6—C2 unit appears to be well supported (341, 342) (Scheme 4). Studies favor a biosynthetic scheme for ephedrine where C6—C, compounds such as benzoic acid or benzaldehyde react with C2—N compounds or equivalents to give ephedrine. The origin of the C2—N unit is still obscure. Methyl groups for N-methylation were previously shown to be donated from methionine or formate (538). 

Stable isotope methodology has been applied to the study of the biosynthesis of madumycin II (A2315A, 92) in Actinoplanes philippensis (60, 64). As with virginiamycin Ml (90), carbons 2, 26, 27, and 28 were found to be derived from valine, C-29 from methionine, C-3 to C-6 from acetate, N-7, C-8, and C-9 from glycine, carbons 10 to 17 and C-31 from acetate, and N-18, C-19, C-20, 0-21, C-32, and 0-34 from serine. The origin of the D-alanine residue, N-23, C-24, C-25, C-35, and 0-36, was of particular interest in this study. No incorporation of DL-[U-13C]serine was observed in the alanine portion of the molecule, eliminating the intermediacy of the a,(3-dehydro alanine unit 101 derivable from the acylserine precursor 100. This was corroborated by the observed incorporation into the molecule of intact doubly labeled L-[3-l3C,3,3,3-2H]alanine. dl-[1-l4C]Alanine was also efficiently incorporated. These results and those from de-... 

Further detail on the biosynthesis of corynoline (78) and related alkaloids is that (76) is a precursor for corynoline (78) and corycavine (77).64 In the latter case it was observed that the configurations at C-13 and C-14 in the precursor were unimportant and incorporation occurred via the metho-salt. Tetrahydro-corysamine (76) is closely related to corydaline, whose biosynthesis from tyrosine and methionine has been studied.66 The C-methyl group at C-13 was shown to arise from methionine and the mechanism suggested for the methylation involves... 

D-Desosamine (51) and D-mycaminose (52) occur in macrolide antibiotics.2 Early studies with tracers showed that the hexose portion of these sugars can be derived from D-glucose without inversion or breakdown of the sugar chain.82,83 The N- methyl groups are derived from methionine.82,84 No further work on the biosynthesis of these sugars has been reported. 

Figure 10 Methylcorrinoids as the source of a methyl group in the biosynthesis of methionine from homocysteine (top), of methane (middle), and of the acetyl group of acetyl coenzyme A (bottom)...

Figure 11 Schematic illustration of the cobalamin-dependent enzymatic biosynthesis of methionine via methyl-group transfer from A -methyltetrahydrofolate to homocysteine...

Methionol derivatives. Methionol, 3-(methylthio)-l-propanol, a well known S-compound in white and red wines was first identified by Muller et al. (77). The biosynthesis of methionol starts from methionine following the Ehrlich-mechanism 18). The sensory properties of methionol are descibed as raw potatoes (77). Not only methionol, but also succinic acid is a normal by-product of alcoholic fermentation. Our studies on volatile compounds in Scheurebe wines revealed for the first time the presence of succinic acid ethyl methionyl ester (5). This compound is characterized... 

Aminocyclopropane carboxylic acid (6) has been detected in several plant tissues a procedure for preparing 6 from agricultural wastes, by extraction with a diluted solution of sulfosalicylic acid, has been described . 6 was established to be an intermediate product in ethylene biosynthesis " . Ethylene acts as a phytohormone which is involved in many metabolic processes in plants, e.g. in ripening, in stress situations or after wounding (see review and references cited therein). Natural 6 is formed from methionine via sulfonium salt (640) only S,S-(640) acted as a substrate for aminocyclopropanecarbo-xylate synthase, the S,R and R,R isomers of 640 were inactive as substrates . 6 can be... 

There is no experimental result to elucidate the biosynthesis of pyrimidobleonic acid moiety at the present time except for the methyl group of the pyrimidine ring, which comes from methionine. Compared with the biosynthesis of lycomarasmin39), the amine component II appears to be derived from aspartylasparagine via dehydrative cyclization, dehydrogenation, amination and methylation (Fig. 13). amino acid + acetate or acetate + C,... 

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