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The Effect of Dietary Cysteine Level on Cysteine Metabolism in Rats¹

Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853

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, ³⁵SO/₄, 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.

KEY WORDS: • cysteine • cysteine desulfhydrase • cysteine dioxygenase • cysteine sulfinate decarboxylase • taurine • sulfate

¹ This research was supported by U.S. Public Health Service research grant AM-26959 and by New York State Hatch Funds.

² To whom reprint requests should be sent.

Manuscript received 28 May 1982.

This article has been cited by other articles:

				M. H. Stipanuk, J. E. Dominy Jr., J.-I. Lee, and R. M. Coloso Mammalian Cysteine Metabolism: New Insights into Regulation of Cysteine Metabolism J. Nutr., June 1, 2006; 136(6): 1652S - 1659S. [Abstract] [Full Text] [PDF]