The effect of dietary cysteine level on cysteine metabolism in rats.
Male, Sprague-Dawley rats were fed L-amino acid diets that contained 0.4% L methionine and either 0, 0.2% (control), or 2.6% L-cysteine (free base) for  5 or 20 days. Hepatic cysteine dioxygenase activity in rats fed 2.6% cysteine was 5 and 3-times as great as in pair-fed control rats at 5 and 20 days, respectively. Cysteine sulfinate decarboxylase activity in liver of rats fed 2.6% cysteine for 20 days was about 40% of the pair-fed control level. The activity of cysteine sulfinate aminotransferase and the rate of cysteine desulfhydration were not influenced by dietary cysteine content. Rats that had been fed these diets for 5 days were intubated with 5 g of diet that contained either 0.2% or 2.6% L-[35S] cysteine. The 24-hour urinary excretion of total 35S, 35SO4, and [35S] taurine by rats that had been fed 2.6% cysteine for 5 days and intubated with 0.2% L[35S] cysteine was 1.4-, 1.8-, and 2.4-fold, respectively, that of pair-fed control rats. About 2.1, 1.8, and 9.1 times as much 35S, 35SO4, and [35S] taurine, respectively, were excreted by rats fed 2.6% cysteine for 5 days and intubated with 2.6% L-[35S] cysteine as was excreted by pair-fed control rats. Urinary excretion of these metabolites was not different between rats fed 0 and 0.2% cysteine. These results indicate that the cysteine sulfinate pathway plays a major regulatory role in the metabolism of excess cysteine.
D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002262:Carboxy-Lyases / Q000378:metabolism*; D003545:Cysteine / Q000008:administration & dosage / Q000378:metabolism*; D050558:Cysteine Dioxygenase; D049308:Dioxygenases; D004305:Dose-Response Relationship, Drug; D008099:Liver / Q000201:enzymology*; D008297:Male; D008954:Models, Biological; D010105:Oxygenases / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013431:Sulfates / Q000378:metabolism; D013654:Taurine / Q000378:metabolism; D000637:Transaminases / Q000378:metabolism*
D013431:Sulfates; D013654:Taurine; D010105:Oxygenases; D049308:Dioxygenases; D050558:Cysteine Dioxygenase; D000637:Transaminases; C019973:cysteine sulfinate transaminase; D002262:Carboxy-Lyases; C019972:sulfoalanine decarboxylase; D003545:Cysteine