Role of a cytochrome P450-dependent monooxygenase in the hydroxylation of 24-epi-brassinolide
作者:Jochen Winter、Bernd Schneider、Dieter Strack、Günter Adam
DOI:10.1016/s0031-9422(96)00827-8
日期:1997.5
24-epi-Brassinolide, exogenously applied to cell suspension cultures of Lycopersicon esculentum is hydroxylated at C-25 and C-26, respectively, followed by glucosylation of the newly formed hydroxyl group. Treatment of the cell cultures with the specific cytochrome P450 inhibitors, clotrimazole and ketoconazole, resulted in a strong decrease of only the C-25 hydroxylation, whereas hydroxylation at C-26 was not affected. The common cytochrome P450 inducers, ethanol, MnCl2, phenobarbital, pregnenolone 16 alpha-carbonitrile or clofibrate, did not induce hydroxylation activity at C-25 or at C-26. In addition, substrate analogues (22S,23S-homobrassinolide, 24-epi-castasterone, ecdysone, and 20-OH-ecdysone) were not accepted. Only application of 24-epi-brassinolide and brassinolide resulted in an increased activity of both the C-25; and C-26 hydroxylases. For further examination of the molecular level of this inducing effect, the influence of the protein biosynthesis inhibitor cycloheximide has been studied. Thus, increase of both hydroxylase activities is obviously based on gene expression by action of the substrates, 24-epi-brassinolide and brassinolide. (C) 1997 Elsevier Science Ltd.