Cysteine biosynthesis from homoserine (WP256)
Saccharomyces cerevisiae
O-Acetyl-L-homoserine sulfhydrylase participates in an alternative pathway of L-homocysteine synthesis. Cysteine can then be produced by the reverse transsulfuration pathway, which involves the conversion of homocysteine to cysteine with the help of a cystathionine intermediate. This process takes place in two steps: First, cystathionine-synthase (Cys4p) catalyzes a -displacement reaction, whereby the thiol group of homocysteine replaces the hydroxyl group of serine, resulting in the formation of cystathionine. Second, cystathionine-lyase (Cys3p) catalyzes an ,-elimination reaction, which hydrolyzes cystathionine to generate cysteine, -ketobutyrate, and ammonia.
Authors
Meredith Braymer , Egon Willighagen , Martina Summer-Kutmon , Susan Coort , Denise Slenter , Alex Pico , and Eric WeitzActivity
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Organisms
Saccharomyces cerevisiaeCommunities
Annotations
Pathway Ontology
cysteine metabolic pathway| Label | Type | Compact URI | Comment |
|---|---|---|---|
| homocysteine | Metabolite | cas:6027-13-0 | |
| cystathionine | Metabolite | cas:56-88-2 | |
| L-cysteine | Metabolite | cas:52-90-4 | |
| acetate | Metabolite | cas:64-19-7 | |
| 2-oxobutanoate | Metabolite | hmdb:HMDB0000005 | |
| NH3 | Metabolite | hmdb:HMDB0000051 | |
| homoserine | Metabolite | cas:672-15-1 | |
| acetyl-CoA | Metabolite | cas:72-89-9 | |
| L-serine | Metabolite | cas:56-45-1 | |
| Coenzyme A | Metabolite | cas:64885-97-8 | |
| CYS4 | GeneProduct | sgd:S000003387 | |
| MET17 | GeneProduct | sgd:S000004294 | |
| MET2 | GeneProduct | sgd:S000005221 | |
| CYS3 | GeneProduct | sgd:S000000010 |