Kline E L, Smith T J, Carland K A, Blackmon B
Department of Microbiology, Clemson University, South Carolina 29634-1909.
J Cell Physiol. 1988 Mar;134(3):497-502. doi: 10.1002/jcp.1041340324.
The effect of estrogens on tyrosinase (EC 1.14.18.1) activity was studied in B16/C3 melanoma cultures. Estradiol, estriol, and other related steroids failed to influence tyrosinase activity when added to the medium of proliferating cultures. Imidazole (10 mM), on the other hand, induced the activity of that enzyme 3-fold, as reported previously. Estradiol and estriol blocked imidazole induction, however, unlike the other estrogenic compounds. The blockade occurred within 15 min of hormone addition and was reversible. Dose-response studies revealed that the maximal estradiol effect occurred at 0.75 nM and the half-maximal effect occurred at 0.5 nM. Estriol was more potent, with the maximal blockade occurring at approximately 0.5 nM and half-maximal effect at 0.25 nM. The induction of tyrosinase by imidazole and the blockade of this induction by estradiol and estriol could not be demonstrated in broken cell preparations, suggesting that direct enzyme activation-inactivation was not involved. Studies utilizing inhibitors of protein and RNA synthesis suggest that this effect is mediated at a pre-translational level and is independent of mRNA destabilization.
在B16/C3黑色素瘤培养物中研究了雌激素对酪氨酸酶（EC 1.14.18.1）活性的影响。当将雌二醇、雌三醇和其他相关类固醇添加到增殖培养物的培养基中时，它们未能影响酪氨酸酶的活性。另一方面，如先前报道的那样，咪唑（10 mM）可使该酶的活性诱导3倍。然而，与其他雌激素化合物不同，雌二醇和雌三醇可阻断咪唑诱导。这种阻断在添加激素后15分钟内发生且是可逆的。剂量反应研究表明，雌二醇的最大效应出现在0.75 nM，半最大效应出现在0.5 nM。雌三醇的效力更强，最大阻断出现在约0.5 nM，半最大效应出现在0.25 nM。在破碎细胞制剂中无法证明咪唑对酪氨酸酶的诱导以及雌二醇和雌三醇对这种诱导的阻断，这表明不涉及直接的酶激活-失活。利用蛋白质和RNA合成抑制剂的研究表明，这种效应是在翻译前水平介导的，并且与mRNA的不稳定无关。
