期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1975
卷号：72
期号：3
页码：1017-1020
DOI：10.1073/pnas.72.3.1017
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Glucocorticoid hormones increase the level of hepatic tryptophan oxygenase (EC 1.13.11.11 ; L-tryptophan:oxygen 2,3-oxidoreductase (decyclizing) by increasing its rate of synthesis. Studies were performed to determine whether this induction is mediated by controlling the level of the mRNA for tryptophan oxygenase of by changing the translational efficiency of a fixed level of mRNA. Activity of tryptophan oxygenase mRNA was quantitated in a Krebs ascites cell-free, protein-synthesizing system, supplemented with tRNA and rabbit reticulocyte initiation factors. De novo synthesis of the protomeric unit(s) of the enzyme was a linear function of the amount of mRNA added. Time course and dose-response studies in which the enzyme level and mRNA activity in livers from rats injected with inducing doses of hydrocortisone were compared indicate that the induction of this enzyme is accompanied by a proportional increase in the level of its mRNA. This was true for mRNA isolated from total liver as well as from cytoplasmic polysomes. Induction of the enzyme by its substrate, tryptophan, however, was not accompanied by a parallel increase in mRNA activity.
