Molecular Cloning, Functional Expression, and Tissue Distribution of a Potato Sprout Allene Oxide Synthase Involved in a 9-Lipoxygenase Pathway
作者:Darika KONGRIT、Mitsuo JISAKA、Kazuhiro KOBAYASI、Yutaka NISHIGAICHI、Kohji NISHIMURA、Tsutomu NAGAYA、Kazushige YOKOTA
DOI:10.1271/bbb.60120
日期:2006.9.23
Potato (Solanum tuberosum) plants are rich in 9-lipoxygenase, which converts linoleic acid and α-linolenic acid to 9S-hydroperoxy-10E,12Z-octadecadienoic acid (9-HPOD) and 9S-hydroperoxy-10E,12Z,15Z-octadecatrienoic acid (9-HPOT) respectively. The allene oxide synthase (AOS) involved in 9-HPOD/9-HPOT metabolism in potato, however, has not been characterized in detail. We cloned a cDNA encoding a novel AOS from potato sprouts by reverse transcriptase-PCR based on a partial sequence in the EST database. This AOS was successfully expressed in the yeast Pichia pastoris, and purified using Ni-NTA resin. The recombinant enzyme metabolized 9-HPOD, 9-HPOT, 13-HPOD, and 13-HPOT with reaction efficiencies of 2.5×107, 1.0×107, 2.5×106, and 7.6×106 M−1 s−1 respectively. The α-ketol formed from 9-HPOD was composed mainly of the 9R-enatimomer (90%). Besides sprouts, the mRNA of this AOS was detected in buds, flowers, and stems, but not in leaves, tubers, or roots of mature plants, suggesting that this enzyme has a tissue-specific function.
马铃薯(Solanum tuberosum)植物富含 9-脂加氧酶,可将亚油酸和 α-亚麻酸分别转化为 9S-hydroperoxy-10E,12Z-ctadecadienoic acid (9-HPOD) 和 9S-hydroperoxy-10E,12Z,15Z-ctadecatrienoic acid (9-HPOT)。然而,参与马铃薯中 9-HPOD/9-HPOT 代谢的氧化异烯合成酶(AOS)尚未得到详细表征。我们根据EST数据库中的部分序列,通过反转录酶-PCR从马铃薯芽中克隆了一个编码新型AOS的cDNA。这种 AOS 在酵母 Pichia pastoris 中成功表达,并用 Ni-NTA 树脂纯化。重组酶代谢了 9-HPOD、9-HPOT、13-HPOD 和 13-HPOT,反应效率分别为 2.5×107、1.0×107、2.5×106 和 7.6×106 M-1 s-1。由 9-HPOD 生成的 α-酮主要由 9R 异构体组成(90%)。除了萌芽外,在成熟植株的芽、花和茎中也检测到了这种 AOS 的 mRNA,但在叶、块茎和根中没有检测到,这表明这种酶具有组织特异性功能。