我们的环境受到四百万以上各种合成化合物的污染。据美国环境保护局(EPA)和食品与药物管理局(FDA)估计,常用的化学物有63000种以上,包括各种药物成分、食品添加剂、农药和头发染料。不溶于水的化学物必须在机体内转变成为极性较强的化合物后才能有效地排泄。这一化学转化是在一类称为药物代谢酶的催化下完成的;药物代谢酶主要存在于肝脏中,但在肺、肾、皮肤和胃肠道中也有。在生物转 Our environment is contaminated with more than four million synthetic compounds. According to estimates by the U.S. Environmental Protection Agency (EPA) and the Food and Drug Administration (FDA), there are more than 63,000 commonly used chemicals, including various pharmaceutical ingredients, food additives, pesticides and hair dyes. Water-insoluble chemicals must be effectively excreted in the body after they have been converted to more polar compounds. This chemical conversion is accomplished under the catalysis of a class of drug-metabolizing enzymes; drug-metabolizing enzymes are found mainly in the liver, but also in the lung, kidney, skin and gastrointestinal tract. In the biological turn