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An investigation into possible xenobiotic-endobiotic inter-relationships involving the amino acid analogue drug, S-carboxymethyl-L: -cysteine and plasma amino acids in humans.
MedLine Citation:
PMID:  21559953     Owner:  NLM     Status:  Publisher    
The amino acid derivative, S-carboxymethyl-L: -cysteine, is an anti-oxidant agent extensively employed as adjunctive therapy in the treatment of human pulmonary conditions. A major biotransformation route of this drug, which displays considerable variation in capacity in man, involves the oxidation of the sulfide moiety to the inactive S-oxide metabolite. Previous observations have indicated that fasted plasma L: -cysteine concentrations and fasted plasma L: -cysteine/free inorganic sulfate ratios were correlated with the degree of sulfoxidation of this drug and that these particular parameters may be used as endobiotic biomarkers for this xenobiotic metabolism. It has been proposed also that the enzyme, cysteine dioxygenase, was responsible for the drug sulfoxidation. Further in this theme, the degree of S-oxidation of S-carboxymethyl-L: -cysteine in 100 human volunteers was investigated with respect to it potential correlation with fasted plasma amino acid concentrations. Extensive statistical analyses showed no significant associations or relationships between the degree of drug S-oxidation and fasted plasma amino acid concentrations, especially with respect to the sulfur-containing compounds, methionine, L: -cysteine, L: -cysteine sulfinic acid, taurine and free inorganic sulfate, also the derived ratios of L: -cysteine/L: -cysteine sulfinic acid and L: -cysteine/free inorganic sulfate. It was concluded that plasma amino acid levels or derived ratios cannot be employed to predict the degree of S-oxidation of S-carboxymethyl-L: -cysteine (or vice versa) and that it is doubtful if the enzyme, cysteine dioxygenase, has any involvement in the metabolism of this drug.
Glyn B Steventon; Stephen C Mitchell; Santigo Angulo; Coral Barbas
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-5-11
Journal Detail:
Title:  Amino acids     Volume:  -     ISSN:  1438-2199     ISO Abbreviation:  -     Publication Date:  2011 May 
Date Detail:
Created Date:  2011-5-11     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9200312     Medline TA:  Amino Acids     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Clinical Medicine Division, Postgraduate Medical School, University of Surrey, Daphne Jackson Road, Manor Park, Guildford, Surrey, GU2 7WG, UK,
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