Cysteine biosynthesis from homoserine (Saccharomyces cerevisiae)
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Description
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.
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| Name | Type | Database reference | Comment |
|---|---|---|---|
| 2-oxobutanoate | Metabolite | HMDB0000005 (HMDB)  | |
| CYS3 | GeneProduct | S000000010 (SGD) | |
| CYS4 | GeneProduct | S000003387 (SGD) | |
| Coenzyme A | Metabolite | 64885-97-8 (CAS) | |
| H2O | Metabolite | ||
| H2S | Metabolite | ||
| L-cysteine | Metabolite | 52-90-4 (CAS) | |
| L-serine | Metabolite | 56-45-1 (CAS) | |
| MET17 | GeneProduct | S000004294 (SGD) | |
| MET2 | GeneProduct | S000005221 (SGD) | |
| NH3 | Metabolite | HMDB0000051 (HMDB) | |
| O-Acetyl-L-homoserine | Metabolite | ||
| acetate | Metabolite | 64-19-7 (CAS) | |
| acetyl-CoA | Metabolite | 72-89-9 (CAS) | |
| cystathionine | Metabolite | 56-88-2 (CAS) | |
| homocysteine | Metabolite | 6027-13-0 (CAS) | |
| homoserine | Metabolite | 672-15-1 (CAS) |
Annotated Interactions
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