代谢
细胞色素P450单加氧酶在除草剂的解毒以及木质素、类黄酮和酚酸类的合成中扮演着至关重要的角色。通过对玉米(Zea mays)幼苗中三唑草酮代谢的生化分析,已经证明负责这种除草剂解毒的P450是由萘酐(NA)诱导的,萘酐是一种植物安全剂,同时三唑草酮本身也能诱导。对不同年龄的幼苗进行的诱导研究表明,有两种不同的响应途径调节这种P-450活性。NA的诱导与幼苗的发育年龄无关,直到6.5天;而三唑草酮的诱导则与发育年龄紧密相关,因为三唑草酮的代谢可以在年轻的(2.5天)幼苗中被三唑草酮诱导,但在较老的(6.5天)幼苗中则不能。当NA与三唑草酮联合施用时,可以协同增强年轻幼苗中三唑草酮的代谢,使其水平显著高于单独使用除草剂或安全剂处理时的水平。在较老的幼苗中,NA加三唑草酮处理只能诱导三唑草酮代谢到与单独NA处理相当的水平,这再次表明,对三唑草酮的诱导级联反应在后期发育中是非功能的。MnCl2的研究表明,较老幼苗对三唑草酮的不敏感并不是由于这种P-450解毒系统的诱导性普遍受限,而是由于三唑草酮响应途径的特定限制。
Cytochrome P450 monooxygenases play paramount roles in the detoxification of herbicides as well as in the synthesis of lignins, flavonoids, and phenolic acids. Biochemical analysis of triasulfuron metabolism in maize (Zea mays) seedlings has demonstrated that the P450(s) responsible for detoxification of this herbicide is induced by naphthalic anhydride (NA), a plant safener, and by triasulfuron, the herbicide itself. Induction studies conducted with seedlings of different ages suggest that two separate response pathways modulate this P-450 activity. Induction by NA is independent of the developmental age of the seedlings up to 6.5 d; induction by triasulfuron is tightly modulated with respect to developmental age in that triasulfuron metabolism can be induced by triasulfuron in young (2.5 d) but not older (6.5 d) seedlings. Induction by NA administered in combination with triasulfuron synergistically enhances triasulfuron metabolism in younger seedlings to levels substantially above that obtained with either herbicide or safener treatment alone. In older seedlings, NA plus triasulfuron treatment induces triasulfuron metabolism to only the level of NA treatment alone, indicating again that the induction cascade responding to triasulfuron is nonfunctional in later development. MnCl2 studies indicate that the triasulfuron insensitivity of older seedlings does not result from a general limitation in the inducibility of this P-450 detoxification system but rather from specific limitations in the triasulfuron-response pathway.
来源:Hazardous Substances Data Bank (HSDB)