Killewich L, Schutz G, Feigelson P
Proc Natl Acad Sci U S A. 1975 Nov;72(11):4285-7. doi: 10.1073/pnas.72.11.4285.
Tryptophan 2,3-dioxygenase [EC 1.13.11.11; L-tryptophan:oxygen 2,3-oxidoreductase (decyclizing)] activity is induced by glucocorticoid hormones and superinduced by actinomycin D. Previous experiments had shown that hormonal induction of the enzyme activity is accompanied by parallel increases in tryptophan 2,3-dioxygenase mRNA level. In this study, we measured the tryptophan 2,3-dioxygenase mRNA levels during superinduction as well as hormonal induction, to determine whether superinduction of the enzyme activity is also mediated through changes in mRNA concentration. Tryptophan 2,3-dioxygenase mRNA was measured in a Krebs ascites cell-free protein synthesizing system supplemented with rabbit reticulocyte initiation factors. We found that during superinduction of the enzyme activity by actinomycin D, the mRNA level is identical to that of the actinomycin D-free controls. Our results do not, therefore, support the hypothesis that hormonal induction and/or superinduction of tryptophan 2,3-dioxygenase mRNA are regulated by a rapidly turning over repressor.
色氨酸2,3-双加氧酶[EC 1.13.11.11；L-色氨酸：氧2,3-氧化还原酶（脱环）]活性由糖皮质激素诱导，并被放线菌素D超诱导。先前的实验表明，该酶活性的激素诱导伴随着色氨酸2,3-双加氧酶mRNA水平的平行升高。在本研究中，我们测量了超诱导以及激素诱导过程中色氨酸2,3-双加氧酶的mRNA水平，以确定酶活性的超诱导是否也通过mRNA浓度的变化介导。在补充有兔网织红细胞起始因子的Krebs腹水无细胞蛋白质合成系统中测量色氨酸2,3-双加氧酶mRNA。我们发现，在放线菌素D对酶活性的超诱导过程中，mRNA水平与无放线菌素D的对照相同。因此，我们的结果不支持色氨酸2,3-双加氧酶mRNA的激素诱导和/或超诱导受快速周转阻遏物调节的假说。
