紅龍果果實發育後期醣類合成酶和蘋果酸去氫酶活性之變化

Changes in the Activities of Sugar Synthesis Enzymes and Malate Dehydrogenase in Hylocereus undatus Fruit during Later Period of Development

本研究分析紅龍果果實發育後期影響果肉糖類累積的數種酵素活性變化，包括酸性蔗糖轉化酶（Acid invertase, AI）、中性蔗糖轉化酶（Neutral invertase, NI）和α-澱粉水解酶（α-amylase）。結果AI及NI活性隨葡萄糖和果糖之累積而上升，在花後25-27天達到最高點，而後再下降。又AI活性遠大於NI，應為醣類累積的關鍵酵素。α-amylase活性隨著果實的成熟而逐漸降低，到花後25天達最低點，之後又再次上升直至花後29天。蘋果酸去氫酶（Malate dehydrogenase, MDH）之活性隨果實生長而逐漸下降。果實內之蘋果酸、檸檬酸和抗壞血酸含量在花後25天達最高；而草酸含量在果實發育後期則呈現持續下降的狀態。AI可能是影響紅龍果果實醣度的關鍵酵素，而MDH對蘋果酸的影響僅在花後23至25天明顯。 Changes in the activities of acid invertase (AI), neutral invertase (NI) and α-amylase, which may affect the accumulation of soluble sugars in pitaya (Hylocereus undatus), were monitored during later stages of fruit development. AI and NI activities increased during fruit development before 25(superscript th)-27(superscript th) day after anthesis. AI activity was greater than NI activity. Therefore, AI might be as the key enzyme associated with a rapid accumulation of glucose in the fruit. α-amylase activity reduced gradually during fruit maturation up to 29(superscript th) day after anthesis. Malate dehydrognase (MDH) activity also declined during fruit development. Malic acid, citric acid and ascorbic acid in the pulp reached highest peak on 25(superscript th) day after anthesis which the concentration of oxalic acid reduced gradually during fruit maturation. AI was considered to be the key enzyme associated with a rapid accumulation of soluble sugars in pitaya fruit. MDH affected malic acid content during 23(superscript th) to 25(superscript th) day after anthesis.