1-胺基環丙烷－1-羧酸合成酶之生化特性及其基因結構

Biochemical Properties and Gene Structure of the 1-Aminocyclopropane-1-carboxylate Synthase

黃鳳琴(Fong-Chin Huang) ； 黃鵬林(Pung-Ling Huang)

《中國園藝》 39卷2期 (1993/06) Pp. 59-66

https://doi.org/10.6964/JCSHS.199306.0059

摘要

乙烯是主要植物荷爾蒙之一，它對植物的生長與發育具有相當廣泛的生理效應。目前已知其生合成途逕爲：甲硫胺酸(methionine)→S-腺苷甲硫胺酸(S-adenosylmethionine, SAM)→1-胺基環丙烷－1-羧酸(1-aminocyclopropane-1-carboxylic acid, ACC)→乙烯(ethylene)。其中SAM轉變成ACC爲速率限制步驟，而ACC合成酶正是擔任催化此步驟之酵素，故ACC合成酶在乙烯合成途逕中扮演著非常重要的角色，是爲一速率限制酵素。本文針對此酵素介紹其性質、構造及其調節的機制，總結如下：ACC合成酶是以多種形式存在的，但其活性部位之胺基酸序列具高度保守性；其分子量大約55 KDa，且以雙元体的方式存在，但在純化的過程中會降解成45 KDa左右；在進行催化時，以維生素六輔酶(pyridoxal phosphate, PLP)爲輔助因子，且具有被其受質SAM失活化之特性：此外ACC合成酶基因是由多重基因所組成，並且解碼(encode)許多異型態之ACC合成酶，其酵素活性可被不同的因子誘發，包括生長素，逆境、癒傷及各種金屬物質，此誘發作用被認爲是由於轉錄作用加強而使蛋白質重新合成。

關鍵字

乙烯 ； ACC合成酶 ； 速率限制酵素 ； 基因表現

並列摘要

Ethylene is a plant hormone that has a wide impact on plant growth and development. Methionine is the biological precursor of ethylene in higher plants, and it is converted to ethylene via the following route: methionine→S-sdenosylmethionine (SAM)→1-aminncyrlopropane-1-carboxylic acid (ACC)→ethylene. The conversion of SAM to ACC is catalyzed by the key regulatory enzyme, ACC synthase (E. C 4.1.1.14), in the biosynthesis of ethylene. This review presents an overview of characteristics, structure and regulation of this enzyme. It shows that there are multiple forms of ACC synthase, bat the active-site peptide reveals highly conserved dodecapeptides; the molecular size of ACC synthase, a dimer, is 55 KDa, and the enzyme is partially degraded to a 45 KDa peptide during purification procedures; it requires pyridoxal phosphate as cofactor, and can be inactivated by its substrate SAM and ACC synthase gene is a gene family, encoding multiple forms of ACC synthase, which ran be induced by a diverse group of inducers, including auxin, stress, wounding, and various metals, and the induction was suggested to be due to enhanced transcription.

並列關鍵字

ethylene ； ACC synthase ； rate-limiting enzyme ； gene expression