Effects of protein, methionine, or chloride on acid-base balance and on cysteine catabolism.
Metabolism of cysteine to sulfate results in production of H+, whereas metabolism of cysteine to taurine does not. Rats were fed a basal low-protein diet or a diet with excess protein, methionine, or chloride for 2-3 wk, and effects of these treatments on acid-base homeostasis and on cysteine metabolism were determined. Hepatocytes from rats fed diets with excess methionine, but not from rats fed diets with excess protein or chloride, catabolized a high proportion of cysteine to taurine (32% vs. 4-7% for other groups), and intact rats fed excess methionine excreted more sulfur as taurine (51% of total sulfur vs. 1-6% for other groups). The formation of taurine vs. sulfate as the end product of cysteine catabolism provides a metabolic compensation that minimizes the acid load in rats fed excess sulfur amino acids. However, increased production of taurine vs. sulfate is not a general adaptive response to acidogenic diets.
D000136:Acid-Base Equilibrium / Q000187:drug effects*; D000818:Animals; D002712:Chlorides / Q000008:administration & dosage / Q000494:pharmacology*; D003545:Cysteine / Q000378:metabolism*; D004032:Diet; D004044:Dietary Proteins / Q000494:pharmacology*; D004435:Eating; D008099:Liver / Q000378:metabolism; D008297:Male; D008715:Methionine / Q000008:administration & dosage / Q000494:pharmacology*; D011506:Proteins / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013431:Sulfates / Q000378:metabolism; D013654:Taurine / Q000378:metabolism; D015430:Weight Gain
D002712:Chlorides; D004044:Dietary Proteins; D011506:Proteins; D013431:Sulfates; D013654:Taurine; D008715:Methionine; D003545:Cysteine