所有有生命的生物体 ,包括人类不断接触到的大约 10 0 0 0多种存在于食物、水源环境中的化学物质 ,许多自然存在的化学物质本身就有毒性 ,生物体依靠体内各种不同的防御机制来保护自身 ,其中 ,特别重要的一种是细胞色素Ｐ4 5 0酶含血红素的单氧化酶 ,该酶催化氧结合有机分子的 All living organisms, including about 10 000 species of chemicals that are in constant contact with humans, exist in food and water environments. Many naturally occurring chemicals are themselves toxic and organisms depend on a variety of different Defense mechanisms to protect themselves, of which a particularly important one is the cytochrome P450 enzyme heme-containing monooxygenase that catalyzes the oxygen-binding organic molecule