Benevenga NJ (1974) Toxicities of methionine and other amino acids.
Stipanuk M (1986) Metabolism of sulfur-containing amino acids.
Homocysteine may either be remethylated to methionine, used for the resynthesis of S-adenosyl- L-homocysteine by reversal of hydrolysis, or irreversibly converted to cystathionine.
in the cysteine/methionine biosynthetic ..
S-adenosyl-L-methionine is then demethylated to produce S-adenosyl-L-homo-cysteine, which is hydrolysed in a reversible reaction to yield homocysteine and adenosine.
Molecular Basis of Cysteine Biosynthesis in Plants - …
Growth on agar plates was monitored by an endpoint, defined as the time when cells were discernibly amassed. The growth delay disappeared with methionine and/or cysteine or both on agar plates () and in liquid BMM (at 18 μg/ml final concentration of each equivalent to 150 μM Cys and 124 μM Met). In contrast to the little benefit of leucine for growth (37 μg/ml final concentration; 282 μM Leu) in liquid BMM (), the striking positive effects of Cys-Met indicated that deficiency of the Cys-Met supply should be the main reason for the growth defect.
Molecular Basis of Cysteine Biosynthesis in Plants
Direct involvement of NdgR in gene expression was examined by considering the genes involved in the very last steps of methionine synthesis (): metF and metE-metH. Two metabolic branches converge to make methionine: a branch to produce the homocysteine moiety from acetyl-serine and the other to provide the methyl-donor from folate. MetF is methylenetetrahydrofolate reductase for converting N5,N10-methylenetetrahydrofolate to N5-methyltetrahydrofolate (H4-folate). MetE and MetH use the methyl group from H4-folate to convert methylate homocysteine to methionine.
E. coli student portal - Cysteine Biosynthesis
Based on the NdgR requirement for proper growth in minimal medium, we looked into the possibility of NdgR involvement in the metabolism of other amino acids. It was a reasonable speculation since LtbR (the NdgR ortholog in Corynebacterium glutamicum) was shown to affect sets of genes for biosynthesis of tryptophan besides BCAA. Amino acid-dependent growth was not characterized in that study, however (). Adopting an empirical approach, we examined 20 individual -amino acids as nutritional supplements to minimal medium (see Fig. S1 in the supplemental material). As minimal medium has 1% glucose and 3 mM (NH4)2SO4, addition of each amino acid at a final concentration of 37 μg/ml was regarded as a minor C/N source in the catabolic process.