鳳梨果實有機酸之代謝

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論文名稱: 鳳梨果實有機酸之代謝
研究生姓名: 劉名旂
指導教授姓名: 陳京城
出版年: 2009
學校名稱: 國立中興大學
系所名稱: 園藝學系所
關鍵字: 鳳梨;有機酸;檸檬酸;蘋果酸;有機酸代謝;pineapple;organic acid;citric aicd;mailc acid;organic acid metabolism
摘要: 本研究以九個品種鳳梨果實為材料,調查其生育期間之有機酸含量變化與其相關代謝酵素活性之關係。結果發現,鳳梨果肉之有機酸含量隨果實發育而上升,至成熟期則會開始下降,此與檸檬酸合成酶(citrate synthase, CS)之活性變化一致。同時於檸檬酸含量提升時,八個品種果實之烏頭酸酶(aconitase, ACO)活性均呈現下降之趨勢,但僅有五個品種可觀察到於檸檬酸含量下降時ACO酵素活性有提高之趨勢。磷酸烯醇丙酮酸羧化酶(Phosphoenolpyruvate carboxylase, PEPC)活性於大部分品種均可觀察到與檸檬酸含量呈負相關,與蘋果酸含量呈正相關,因此在鳳梨果實中有機酸含量之變化與其關係十分密切。 以'台農17號'鳳梨果實為材料,以溫湯處理及冷藏處理,結果發現於35-40℃溫湯處理時,主要影響有機酸含量變化之酵素為蘋果酸酵素(malic enzyme, ME),而當溫湯處理溫度提高至40-45℃時,則轉變為PEPC及粒線體ACO為主要影響之酵素。於8℃冷藏期間PEPC與有機酸含量之關係較為顯著,而於12℃冷藏時,蘋果酸去氫酶(malate dehydrogenase, MDH)之活性亦有顯著相關性,此外,細胞質ME活性於冷藏期間下降,亦可能造成蘋果酸含量上升,因此,MDH及細胞質ME可能為造成蘋果酸含量上升之原因,但整體有機酸含量之上升主要應仍受PEPC所調控。 PEPC酵素可能於鳳梨果實之有機酸代謝扮演著舉足輕重的角色。在檸檬酸含量變化方面,則CS及ACO酵素亦有所影響。在蘋果酸含量變化方面,則MDH及NADP-ME酵素可能扮演重要的角色。The correlation between organic acid contents and organic acid metabolizing enzyme activities in fruits of nine pineapple cultivars were studied. The results showed that organic acid contents increased during early stage of fruit development and decreased after mature stage,which coincided with the chagne of citrate synthase (CS) activities. When citric acid (CA) contents increased, aconitase (ACO) activities decreased in eight pineapple cultivars and when CA contents decreased, ACO acitivities increased in five pineapple cultivars. There were significant negative correlations between phosphoenolpyruvate carboxylase(PEPC) activity and CA contents and there were significant positive correlations between PEPC activity and malic acid (MA) contents. The results suggest that PEPC might play an important role on total organic acid metabolism in pineapple fruit. 'Tainung-17' pineapple fruits were treated with hot water dipping or cold storage and the results showed that malic enzyme (ME) was the main enzyme determining the organic acid contents in 35-40℃ hot water dipping treatments, but when temperature of hot water dipping raised to 40-45℃, the main enzymes were PEPC and mitochondria-aconitase (mACO). During cold storage (8℃), the main enzyme related to organic acid contents was PEPC, and in the treatment of 12℃ cold storage, malate dehydrogenase (MDH) might also effect the acid contents. A decrease in cytosolic-ME activity accompanied with an increase in MA content during cold storage. It suggests that MDH and cytosolic-ME aree the main enzyme for MA metabolism. Overall, PEPC might be the main enzyme for determining the organic acid contents in pineapple fruits. CS and ACO can affect the CA contents and MA contents was effected by MDH and cytosolic-ME during cold storage.
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