Excretion of 3-mercaptolactate-cysteine mixed disulfide, sulfate and taurine in human urine before and after oral administration of sulfur-containing amino acids.
The excretion of 3-mercaptolactate-cysteine mixed disulfide [S-(2-hydroxy-2-carboxyethylthio)-L-cysteine, HCETC], sulfate and taurine in the urine of normal adults was investigated before and after oral administration of L-cysteine and related sulfur-containing amino acids. Before the loading of amino acids, the excretion (mean +/- SD) per kg of body weight per day of HCETC, free sulfate and taurine was 0.096 +/- 0.042, 305.7 +/- 66.1 and 31.9 +/- 8.7 mumols, respectively. After the loading of L-cysteine (800 mumols/kg of body weight), the average excretion in the 24-h urine of HCETC increased 2-fold and that of taurine increased 1.6-fold. The average excretion of free sulfate after the L-cysteine loading was 989.4 +/- 145.1 and 388.8 +/- 51.6 mumols/kg per day in the first and second 24-h urine, respectively, indicating that the sulfur corresponding to 85% of the L-cysteine loaded was excreted as free sulfate in 24 h. Administration of L-cystine (400 mumols/kg) resulted in similar results. The increase in HCETC after L-cysteine or L-cystine administration indicates that L-cysteine is metabolized in part through the transamination pathway (3-mercaptopyruvate pathway) and that an equilibrium exists between the intake and excretion of sulfur in humans.
Yuasa
S
S
Department of Biochemistry, Okayama University Medical School, Japan.
Akagi
R
R
Ubuka
T
T
Masuoka
N
N
Yao
K
K
D000284:Administration, Oral; D000328:Adult; D000603:Amino Acids, Sulfur / Q000008:administration & dosage / Q000493:pharmacokinetics*; D003545:Cysteine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000652:urine; D003553:Cystine / Q000008:administration & dosage / Q000493:pharmacokinetics; D006801:Humans; D008297:Male; D013431:Sulfates / Q000652:urine*; D013654:Taurine / Q000652:urine*
D000603:Amino Acids, Sulfur; D013431:Sulfates; C001705:beta-mercaptolactate cysteine disulfide; D013654:Taurine; D003553:Cystine; D003545:Cysteine