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自然条件下生长的菠萝植株，其叶片的ＰＥＰ羧激酶的脱羧与可逆羧化活性于中午１２时达最大值。脱羧／羧化比值在上午明显高于下午和晚上。脱羧反应底物ＯＡＡ含量于夜间增高，至次日早晨６时最高，随后下降。白天的ＯＡＡ／Ｍａｌ值高于夜间。参与Ｍａｌ及ＯＡＡ形成转化的ＰＥＰＣ和ＭＤＨ活性的昼夜变化与ＰＥＰ羧激酶（ＰＥＰＣＫ）活性的图式相似。ＰＥＰ羧激酶脱羧反应的另一底物ＡＴＰ在夜间０～６时内处于低水平，白天９～１５时内则显著增高。
In pineapple plants grown under natural conditions, the decarboxylation and reversible carboxylation activity of PEP carboxykinase at their leaves reached their maximum at 12 noon. Decarboxylation / carboxylation ratio was significantly higher in the morning than in the afternoon and evening. The content of OAA in decarboxylation reaction increased at night, reaching the highest at 6:00 the next day and then decreased. Daytime OAA / Mal values were higher than at night. The diurnal variations of the PEPC and MDH activities involved in the formation of transformed Mal and OAA are similar to the patterns of PEP carboxykinase (PEPCK) activity. ATP, another substrate for decarboxylation of the PEP carboxykinase, is at a low level during 0-6 hours of the night and significantly increases at 9-15 days during the day.