Morikawa T, Mizutani M, Ohta D
Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai 599-8531, Japan.
Biochem Soc Trans. 2006 Dec;34(Pt 6):1202-5. doi: 10.1042/BST0341202.
Sterols are isoprenoid-derived lipids that are produced via the mevalonate pathway and are involved in various cellular functions in eukaryotes such as maintenance of membrane integrity and biosynthetic precursors of steroid hormones. Among cellular sterols, Delta(22)-sterols containing a double bond at C-22 in the sterol side chain specifically occur in fungi (ergosterol) and plants (stigmasterol and brassicasterol), and several lines of experimental evidence have suggested specific physiological roles of Delta(22)-sterols in plants. Fungal cytochrome P450 (P450), CYP61, has been established as the sterol C-22 desaturase functioning at the penultimate step in the ergosterol biosynthetic pathway. On the other hand, no particular sequence has been assigned as to the enzyme responsible for the introduction of the double bond into the sterol side chain in plants. In this review, we summarize our recent findings demonstrating that CYP710A P450 family genes encode the plant sterol C-22 desaturases to produce stigmasterol and brassicasterol/crinosterol from beta-sitosterol and 24-epi-campesterol respectively.
甾醇是类异戊二烯衍生的脂质，通过甲羟戊酸途径产生，参与真核生物的各种细胞功能，如维持膜完整性和作为甾体激素的生物合成前体。在细胞甾醇中，甾醇侧链C-22位含有双键的Δ(22)-甾醇特异性存在于真菌（麦角甾醇）和植物（豆甾醇和油菜甾醇）中，并且有几条实验证据表明Δ(22)-甾醇在植物中具有特定的生理作用。真菌细胞色素P450（P450）CYP61已被确定为在麦角甾醇生物合成途径倒数第二步起作用的甾醇C-22去饱和酶。另一方面，尚未确定负责在植物甾醇侧链中引入双键的酶的具体序列。在本综述中，我们总结了我们最近的发现，即CYP710A P450家族基因编码植物甾醇C-22去饱和酶，分别从β-谷甾醇和24-表油菜甾醇产生豆甾醇和油菜甾醇/环甾醇。
