Induction and activation of cysteine oxidase of rat liver II. The measurement of cysteine metabolism in vivo and the activation of in vivo activity of cysteine oxidase

• Published in: Biochimica et biophysica acta. General subjects Vol. 297; no. 1; pp. 48 - 59
• Main Authors: Yamaguchi, Kenji, Sakakibara, Shigeki, Asamizu, Juro, Ueda, Iwao
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.1973
• ISSN: 0304-4165; 1872-8006
• DOI: 10.1016/0304-4165(73)90048-2

1. 1. The incorporation of 14C into expired CO 2 from DL-[3- 14C]cysteine injected intraperitoneally into rats was slightly decreased by a loading dose of D-cysteine, whereas either the incorporation from DL-[1- 14C]cysteine or L-[U- 14C]-cysteine was unaffected by this loading. 2. 2. The incorporation of 14C into CO 2 from DL[1- 14C]cysteine or L-[U- 14C]-cysteine was remarkably elavated by L-cysteine loading. 3. 3. Hepatic cysteine oxidase activity was markedly induced by L-cysteine injection but cysteine desulfhydrase activity was not affected. 4. 4. The expected maximum 14CO 2 expirations expressed as C max and the C max half-times for DL-[1- 14C]cysteine, DL-[3- 14C]cysteine and L-[U- 14C]cysteine injected were calculated from the kinetics of 14CO 2 expiration as a function of time. 5. 5. The metabolic distributions of L-cysteine catabolism was calculated from these C max values; L-cysteine is metabolized 31% via the pyruvate pathway and 69% via the taurine pathway. 6. 6. Urinary excretion of 35S from L-[ 35S]cysteine injected was also examined. 7. 7. The facts presented in this paper strongly suggest that the degradation of L-cysteine is metabolized mainly through cysteine sulfinate, and therefore the incorporation of 14CO 2 into expired CO 2 from L-[U- 14C]cysteine is a reflection of the in vivo activity of cysteine oxidase and that the in vivo activity of cysteine oxidase was markedly enhanced by L-cysteine loading but not by D-cysteine loading.