Silva M H, Wixtrom R N, Hammock B D
State of California, Department of Food and Agriculture, Medical Toxicology Branch, Sacramento 95814.
Cancer Res. 1988 Mar 15;48(6):1390-7.
Epoxide hydrolases (EC 3.3.2.3) (EH) are hydrolytic enzymes which may play an important role in the activation and detoxification of mammary carcinogens. In this study, microsomal, cytosolic, and cholesterol epoxide hydrolases along with glutathione S-transferase were characterized in liver and mammary gland from nulliparous and lactating BALB/c mice and from mice transplanted with preneoplastic hyperplastic outgrowths. Clofibrate, butylated hydroxyanisole, and beta-naphthoflavone were used to induce EH. Significant epoxide hydrolysis was observed in microsomal and cytosolic subcellular fractions assayed with cis- and trans-stilbene oxide, benzo(a)pyrene-4,5-oxide, and cholesterol epoxide. The hydrolysis rates were significantly different for nulliparous and lactating animals, in both mammary gland and liver. Clofibrate increased the activity of all forms of EH in liver, but not mammary gland. Butylated hydroxyanisole and beta-naphthoflavone appeared to induce cytosolic glutathione S-transferase as well as some, but not all, forms of EH in liver and mammary gland regardless of hormonal stimuli. The inducers produced different effects in mammary gland as compared with liver. This may be due to either differing amounts of inducer reaching the target site or different regulation of the enzymes in mammary gland and liver. Hyperplastic outgrowths and liver from hyperplastic outgrowth-transplanted animals demonstrated significantly different EH and cytosolic glutathione S-transferase activities from those of nulliparous and lactating animals. This observation offers preliminary evidence that levels of epoxide-metabolizing enzymes are altered when mammary tissue is transformed. Mammary gland cytosolic EH was purified by affinity chromatography and compared to that from liver by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Western blotting, enzyme-linked immunosorbent assay, isoelectric focusing, and enzyme inhibition by 4-phenylchalcone oxide. Cytosolic EH from the mammary gland appears to be identical to the liver enzyme by all the above mentioned biochemical and biophysical parameters.
环氧化物水解酶（EC 3.3.2.3）（EH）是水解酶，可能在乳腺致癌物的活化和解毒过程中发挥重要作用。在本研究中，对未生育和哺乳期的BALB/c小鼠以及移植了癌前增生性赘生物的小鼠的肝脏和乳腺中的微粒体、胞质和胆固醇环氧化物水解酶以及谷胱甘肽S-转移酶进行了表征。使用氯贝丁酯、丁基羟基茴香醚和β-萘黄酮诱导EH。在用顺式和反式芪氧化物、苯并(a)芘-4,5-氧化物和胆固醇环氧化物测定的微粒体和胞质亚细胞组分中观察到显著的环氧化物水解。在乳腺和肝脏中，未生育和哺乳期动物的水解速率存在显著差异。氯贝丁酯增加了肝脏中所有形式的EH的活性，但未增加乳腺中的活性。丁基羟基茴香醚和β-萘黄酮似乎诱导了肝脏和乳腺中的胞质谷胱甘肽S-转移酶以及部分（但不是全部）形式的EH，而与激素刺激无关。与肝脏相比，诱导剂在乳腺中产生了不同的效果。这可能是由于到达靶位点的诱导剂数量不同，或者是乳腺和肝脏中酶的调节方式不同。增生性赘生物以及移植了增生性赘生物的动物的肝脏显示出与未生育和哺乳期动物显著不同的EH和胞质谷胱甘肽S-转移酶活性。这一观察结果提供了初步证据，表明当乳腺组织发生转化时，环氧化物代谢酶的水平会发生改变。通过亲和色谱法纯化了乳腺胞质EH，并通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳、蛋白质印迹法、酶联免疫吸附测定、等电聚焦以及4-苯基查尔酮氧化物的酶抑制作用与肝脏中的EH进行了比较。根据上述所有生化和生物物理参数，乳腺胞质EH似乎与肝脏酶相同。
