Registration Dossier
Registration Dossier
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EC number: 200-296-3 | CAS number: 56-89-3
Basic toxicokinetics
Administrative data
- Endpoint:
- basic toxicokinetics
- Type of information:
- not specified
- Adequacy of study:
- key study
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- other: Data from handbook or data collection
Data source
Reference
- Reference Type:
- review article or handbook
- Title:
- Amino acids from chemical group 34, Flavouring Group Evaluation 26, Revision 1
- Author:
- AFC (EFSA)
- Year:
- 2 008
- Bibliographic source:
- The EFSA Journal, 790, 1-51
Materials and methods
Test guideline
- Qualifier:
- no guideline followed
Test material
- Reference substance name:
- Cystine
- EC Number:
- 200-296-3
- EC Name:
- Cystine
- Cas Number:
- 56-89-3
- Molecular formula:
- C6H12N2O4S2
- IUPAC Name:
- cystine
Constituent 1
Results and discussion
Main ADME results
- Type:
- other:
- Results:
- L-Cystine metabolic pathway
Applicant's summary and conclusion
- Conclusions:
- L-Cystine is converted to L-cysteine through cystine reductase, which requires NADH as cofactor.
L-Cysteine is the central compound in sulfur metabolism in the human body. In proteins the for-mation of disulfide bonds between the thiol groups of cysteine plays an important role for tertiary structure and enzymatic activity, Cysteine is however always incorporated in the polypeptide chain as cysteine.
L-Cysteine is degraded to pyruvate in two steps, one is removal of sulphur and the other is a transamination. Cysteine can be metabolised to form taurine and carbon dioxide through the cys-teinsulfinate pathway, where the initial step is oxidation of cysteine to cysteine sulfinate. This step is catalysed by cysteine dioxygenase. Cysteine sulfinate may then be decarboxylated to form taurine or it may be metabolised via the putative intermediate beta-sulfinylpyruvate to pyruvate and sulfite and then to carbondioxide and sulfate (Stipanuk, 1986). D-Cysteine is not metabolised to taurine (Cavallini et al., 1958; Krijgsheld et al., 1981). - Executive summary:
L-Cystine is converted to L-cysteine through cystine reductase, which requires NADH as cofactor.
L-Cysteine is the central compound in sulfur metabolism in the human body. In proteins the for-mation of disulfide bonds between the thiol groups of cysteine plays an important role for tertiary structure and enzymatic activity, Cysteine is however always incorporated in the polypeptide chain as cysteine.
L-Cysteine is degraded to pyruvate in two steps, one is removal of sulphur and the other is a transamination. Cysteine can be metabolised to form taurine and carbon dioxide through the cys-teinsulfinate pathway, where the initial step is oxidation of cysteine to cysteine sulfinate. This step is catalysed by cysteine dioxygenase. Cysteine sulfinate may then be decarboxylated to form taurine or it may be metabolised via the putative intermediate beta-sulfinylpyruvate to pyruvate and sulfite and then to carbondioxide and sulfate (Stipanuk, 1986). D-Cysteine is not metabolised to taurine (Cavallini et al., 1958; Krijgsheld et al., 1981).
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