羟脂是从脂肪酸产生的具有生物活性的脂类。在植物中，羟脂通道产生前列腺素一样的、被称为茉莉酮酸的植物激素，同时产生能抵抗压力和使水果及蔬菜具有其特有香味的绿叶挥发物。
现在，羟脂通道酶“丙二烯氧化合酶”（AOS）（呈自由状态，与基质相结合）的晶体结构已被确定。该结构显示了这种酶是怎样控制关键中间体的活性的，并且说明，AOS活性点（与茉莉酮酸的合成有关）上关键氨基酸的突变可将其转变成一种过氧化物裂解酶（合成绿叶挥发物的酶）。另外，比较研究表明，羟脂生物合成基因存在于植物和动物的最后共同祖先中，但在演化过程中在除少数几个后生动物分支以外的所有动物身上都丢失了。（生物谷Bioon.com）
生物谷推荐原始出处：
Nature 455, 363-368 (18 September 2008) | doi:10.1038/nature07307
Structural insights into the evolutionary paths of oxylipin biosynthetic enzymes
Dong-Sun Lee, Pierre Nioche, Mats Hamberg & C. S. Raman
The oxylipin pathway generates not only prostaglandin-like jasmonates but also green leaf volatiles (GLVs), which confer characteristic aromas to fruits and vegetables. Although allene oxide synthase (AOS) and hydroperoxide lyase are atypical cytochrome P450 family members involved in the synthesis of jasmonates and GLVs, respectively, it is unknown how these enzymes rearrange their hydroperoxide substrates into different products. Here we present the crystal structures of Arabidopsis thaliana AOS, free and in complex with substrate or intermediate analogues. The structures reveal an unusual active site poised to control the reactivity of an epoxyallylic radical and its cation by means of interactions with an aromatic -system. Replacing the amino acid involved in these steps by a non-polar residue markedly reduces AOS activity and, unexpectedly, is both necessary and sufficient for converting AOS into a GLV biosynthetic enzyme. Furthermore, by combining our structural data with bioinformatic and biochemical analyses, we have discovered previously unknown hydroperoxide lyase in plant growth-promoting rhizobacteria, AOS in coral, and epoxyalcohol synthase in amphioxus. These results indicate that oxylipin biosynthetic genes were present in the last common ancestor of plants and animals, but were subsequently lost in all metazoan lineages except Placozoa, Cnidaria and Cephalochordata.
