Sweet Potato Storage Root Thioredoxin h2 with Both Dehydroascorbate Reductase and Monodehydroascorbate Reductase Activities

甘藷塊根中硫氧化還原蛋白h2具有去氫抗壞血酸還原酶和單去氫抗壞血酸還原酶的活性

黃冠中(Guan-Jhong Huang) ； 陳顯榮(Hsien-Jung Chen) ； 張永勳(Yuan-Shiun Chang) ； 陸德齡(Te-Ling Lu) ； 林耀輝(Yaw-Huei Lin)

《Botanical Studies》 49卷1期 (2008/01) Pp. 1-7

摘要

在大腸桿菌(M15)中大量表現重組蛋白質硫氧化還原蛋白h2(Trx h2)，利用鎳離子螯合之親和性管柱純化。Trx h2經SDS-PAGE分析其分子量約為1.4kDa。Trx h2在含有穀胱甘肽時，去氫抗壞血酸(dehydroascorbate, DHA)含量會降低而生成抗壞血酸(ascorbate, AsA)。但是，在不含有穀胱甘肽時，Trx h2只有非常低DHA reductase活性。AsA經由AsA氧化酶氧化生成單去氫抗壞血酸(monodehydroascorbate, MDA)自由基。MDA也可經由Trx h2而降低了AsA生成，在NADH存在時模仿MDA reductase催化反應。這結果建議，Trx h2同時具有去氫抗壞血酸還原酶和單去氫抗壞血酸還原酶的活性。

關鍵字

甘藷塊根 ； 硫氧化還原蛋白h2 ； 去氫抗壞血酸還原酶 ； 單去氫抗壞血酸還原酶

並列摘要

Recombinant thioredoxin h (Trx h2) overproduced in E. coli (M15) was purified by Ni(superscript 2+)-chelate affinity chromatography as previously reported (Huang et al., 2004a). The molecular mass of Trx h2 was ca. 14 kDa determined by SDS (sodium dodecyl sulfate)-PAGE (polyacrylamide gel electrophoresis). It had antioxidant activity (Huang et al., 2004b) and it reduced dehydroascorbate (DHA) in the presence of glutathione to regenerate ascorbate (AsA). However, without glutathione, Trx h2 had very low DHA reductase activity. AsA was oxidized by AsA oxidase to generate monodehydroascorbate (MDA) free radicals. MDA was also reduced by Trx h2 to AsA in the presence of NADH mimicking the MDA reductase catalyzed reaction. These data suggest that Trx h2 has both DHA reductase and MDA reductase activities.

並列關鍵字

Dehydroascorbate reductase ； Monodehydroascorbate reductase ； Sweet potato storage roots ； Thioredoxin h