Sharkey Thomas D, Yeh Sansun
Department of Botany, University of Wisconsin, Madison, Wisconsin 53706; e-mail:
Annu Rev Plant Physiol Plant Mol Biol. 2001 Jun;52:407-436. doi: 10.1146/annurev.arplant.52.1.407.
Very large amounts of isoprene are emitted from vegetation, especially from mosses, ferns, and trees. This hydrocarbon flux to the atmosphere, roughly equal to the flux of methane, has a large effect on the oxidizing potential of the atmosphere. Isoprene emission results from de novo synthesis by the deoxyxylulose phosphate/methyl erythritol 4-phosphate pathway in plastids. Dimethylallyl pyrophosphate made by this pathway is converted to isoprene by isoprene synthase. Isoprene synthase activity in plants has a high pH optimum and requirement for Mg2+ that is consistent with its location inside chloroplasts. Isoprene emission costs the plant significant amounts of carbon, ATP, and reducing power. Researchers hypothesize that plants benefit from isoprene emission because it helps photosynthesis recover from short high-temperature episodes. The evolution of isoprene emission may have been important in allowing plants to survive the rapid temperature changes that can occur in air because of the very low heat capacity of isoprene relative to water.
大量的异戊二烯从植被中释放出来，尤其是从苔藓、蕨类植物和树木中。这种进入大气的碳氢化合物通量大致与甲烷通量相当，对大气的氧化潜力有很大影响。异戊二烯的排放源于质体中磷酸脱氧木酮糖/甲基赤藓糖醇4-磷酸途径的从头合成。该途径产生的二甲基烯丙基焦磷酸通过异戊二烯合酶转化为异戊二烯。植物中的异戊二烯合酶活性具有较高的最适pH值，并且对Mg2+有需求，这与其在叶绿体中的位置一致。异戊二烯的排放使植物消耗大量的碳、ATP和还原力。研究人员推测，植物从异戊二烯排放中受益，因为它有助于光合作用从短期高温事件中恢复。由于异戊二烯相对于水的热容量非常低，异戊二烯排放的进化可能在使植物能够在空气中可能发生的快速温度变化中生存方面起到了重要作用。
