Studies on the Properties and Bio-Functions of Prenyl Epoxidase

7- o -甲基叶黄素（7- o -甲基叶黄素）在pH为7.5的缓冲溶液中无酶地缓慢转化为相应的二氢呋喃衍生物，并与6-PN （6-PN）预孵育20小时的灰葡萄孢粗蛋白提取物催化环氧化7- o -甲基叶黄素。未经6-PN预孵育的无细胞提取液制备的菌丝几乎没有环氧化活性。这些事实表明底物类似物6-PN的作用不是酶稳定剂，而是酶诱导剂。酶的反应依赖于双原子氧和NADPH。低剂量的FAD是酶活性最大化所必需的。由于酶活性不受除一氧化碳和细胞色素c外的几种细胞色素P-450抑制剂的抑制，该酶似乎不属于依赖于细胞色素P-450的单加氧酶组，而属于依赖于FAD的单加氧酶组。虽然在125,000 g的上清液中发现了大约一半的总酶活性，但125,000 g颗粒的环氧化反应的比活性比可溶性部分高（x 3.7）。还用不同位置和数目的戊烯基异黄酮检测了底物特异性。并与其他黄蛋白单加氧酶和戊烯基环化酶在植物抗菌素生物合成中的作用进行了比较，讨论了目前依赖于FAD的戊烯基类黄酮环氧化酶的一些特性。在此基础上，对真菌类黄酮代谢及相关植物抗毒素进行了综述，从生物学角度对微生物和植物中烯酰化类黄酮代谢进行了探讨。

Crude protein extracts from Botrytis cinerea preincubated with 6-prenylnaringenin (6-PN) for 20 hr catalyzed the prenyl epoxidation of 7-O-methyl-luteone, The resulting epoxide was non-enzymatically and slowly converted into the corresponding dihydrofurano derivative in a buffer solution at pH 7.5. Preparation of cell-free extracts in the presence of 6-PN from the mycelia without preincubation with 6-PN hardly showed the epoxidizing activity. These facts revealed that the substrate analogue 6-PN took a role not as an enzyme stabilizer, but as an enzyme inducer. The enzyme reaction depends on diatomic oxygen and NADPH.Low amounts of FAD are necessary for maximal enzyme activity. Because the enzymatic activity was not inhibited by several inhibitors of cytochrome P-450 in addition to carbon monooxide and cytochrome c, this enzyme seems to belong not to the monooxygenase group dependent on cytochrome P-450, but to that dependent on FAD.Although about half of the total enzyme activity was found in the 125,000 g supernatant, the specific activity for the epoxidation reaction of 125,000 g pellets was higher (x 3.7) than that of the soluble fraction. Substrate specificity was also examined using someprenylisoflavones differing in position and number of prenyl substitution. Some properties of the present prenylflavonoid epoxidase dependent on FAD was discussed in comparison with otherflavoprotein monooxygenases and prenyl cyclization enzymes concerning phytoalexin biosynthesis.In addition to these research results, a review article "Fungal metabolism of flavonoids and related phytoalexins" was described to discuss the biological aspects of prenylated flavonoid metabolisms in microorganisms and plants.