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Aquifex aeolicus VF5 Pathway: methionine degradation I (to homocysteine)

Pathway diagram: methionine degradation I (to homocysteine)

If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.

Locations of Mapped Genes:

Schematic showing all replicons, marked with selected genes

Superclasses: Degradation/Utilization/Assimilation Amino Acids Degradation Proteinogenic Amino Acids Degradation L-methionine Degradation

Pathway Summary from MetaCyc:
In the degradation pathway shown here, L-methionine is first metabolized toS-adenosyl-L-methionine (SAM), a compound that mediates most biological methylations. In the second reaction, the S-methyl group is transferred to other acceptors in a transmethylation step. The product, S-adenosyl-L-homocysteine, is then hydrolyzed to L-homocysteine and adenosine.

L-homocysteine is a branch point. In rats and humans approximately half of the homocysteine formed is remethylated back to methionine via two salvage pathways, one involving methionine synthase (EC 2.1.1.13), and the other involving betaine-homocysteine S-methyltransferase (EC 2.1.1.5) (see L-methionine salvage from L-homocysteine).

The remainder of the homocysteine is degraded further. The first step is the condensation with serine to form L-cystathionine. cystathionine γ-lyase catalyzes cleavage of the C-γ-S bond of L-cystathionine, yielding L-cysteine, 2-oxobutanoate and ammonia in a transsulfuration reaction (see L-cysteine biosynthesis III (from L-homocysteine)) [Griffith87, Finkelstein90].

Pathway Evidence Glyph:

Pathway evidence glyph

Key to pathway glyph edge colors: ?

  An enzyme catalyzing this reaction is present in this organism
  No enzyme catalyzing this reaction has been identified in this organism
  The reaction and any enzyme that catalyzes it (if one has been identified) is unique to this pathway

Credits:
Created in MetaCyc 15-Mar-1999 by Wagg J , SRI International
Revised in MetaCyc 13-Sep-2006 by Caspi R , SRI International
Imported from MetaCyc 08-Aug-2014 by Subhraveti P , SRI International


References

Finkelstein90: Finkelstein JD (1990). "Methionine metabolism in mammals." J Nutr Biochem 1(5);228-37. PMID: 15539209

Griffith87: Griffith OW (1987). "Mammalian sulfur amino acid metabolism: an overview." Methods Enzymol 143;366-76. PMID: 3309559

Other References Related to Enzymes, Genes, Subpathways, and Substrates of this Pathway

Latendresse13: Latendresse M. (2013). "Computing Gibbs Free Energy of Compounds and Reactions in MetaCyc."


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Page generated by SRI International Pathway Tools version 19.0 on Fri Aug 28, 2015, BIOCYC14A.