Tryptophan pyrrolase in haem regulation. Experiments with administered haematin and the relationship between the haem saturation of tryptophan pyrrolase and the activity of 5-aminolaevulinate synthase in rat liver.
1. Administration of haematin to rats decreases 5-aminolaevulinate synthase activity in whole liver homogenates. 2. An inverse relationship between this decrease and the increase in saturation of apo-(tryptophan pyrrolase) with haem is observed during the initial phase of treatment with haematin. 3. Significant changes in both functions are caused by a 1 mg/kg dose of haematin, whereas the maximum effects are achieved by the 5 mg/kg dose. 4. Prevention by allopurinol of the conjugation of exogenously administered haematin with apo-(tryptophan pyrrolase) renders this haem available for further repression of 5 aminolaevulinate synthase. 5. The various aspects of the relationship between synthase activity and the haem saturation of tryptophan pyrrolase are discussed.
D000624:5-Aminolevulinate Synthetase / Q000378:metabolism*; D000493:Allopurinol / Q000494:pharmacology; D000818:Animals; D004305:Dose-Response Relationship, Drug; D006418:Heme / Q000031:analogs & derivatives* / Q000378:metabolism*; D006427:Hemin / Q000494:pharmacology*; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D051381:Rats; D013217:Starvation / Q000201:enzymology; D014366:Tryptophan Oxygenase / Q000378:metabolism*
D006418:Heme; D000493:Allopurinol; D006427:Hemin; D014366:Tryptophan Oxygenase; D000624:5-Aminolevulinate Synthetase