FB2026_01 , released March 12, 2026
FB2026_01 , released March 12, 2026
Pathway: L-CYSTEINE BIOSYNTHESIS
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General Information
Name
L-CYSTEINE BIOSYNTHESIS
Species
D. melanogaster
Symbol
LCYSBI
FlyBase ID
FBgg0002173
Date last reviewed
2025-01-27
Number of members
2
Description
Description
L-cysteine biosynthesis, also known as the transsulfuration pathway, occurs in the cytosol and converts L-homocysteine, a metabolite derived from L-methionine metabolism, to L-cysteine. Besides its role in protein biosynthesis, L-cysteine is also a precursor for glutathione, taurine, hypotaurine and hydrogen sulfide (H2S) production. It is involved in the synthesis of Mo-molybdopterin cofactor, Iron-Sulfur (Fe-S) cluster assembly and coenzyme A. (Adapted from PMID:31460700 and PMID: 29530337.)
Notes

In the reduced environment of the cytosol, L-cysteine exists as a monomer. However, in organelles, such as lysosomes, and in extracellular spaces, L-cysteine is oxidised to form a disulfide bond linked-dimer, known as cystine.

Source Material
The L-CYSTEINE BIOSYNTHESIS Gene Group has been compiled using the following publication(s): Kabil et al., 2011 .
Key Gene Ontology (GO) terms
Biological Process
L-cysteine biosynthetic process
Cellular Component
cytosol
Related Gene Groups
Parent group(s)
AMINO ACID METABOLISM
GO Causal Activity Model (GO-CAM)
Members (2)
For all members:
GO ribbon stack
 molecular functionbiological processcellular component
External Data
Other resource(s)
Note: The Drosophila pathways shown at these resources are computed using different methods. They may therefore differ from the manually curated and verified pathway shown above.

[FlyCyc: L-cysteine biosynthesis III (from L-homocysteine)](https://biocyc.org/pathway?orgid=DMEL&id=HOMOCYSDEGR-PWY)

[Reactome: Cysteine formation from homocysteine](https://reactome.org/PathwayBrowser/#/R-DME-1614603)

[ KEGG:Cysteine and methionine metabolism](https://www.kegg.jp/pathway/dme00270)

Synonyms and Secondary IDs
Synonym(s)
LCYSBI
L-CYSTEINE BIOSYNTHESIS
transsulfuration pathway
Secondary FlyBase ID(s)
References (2)