几种离子对豇豆根瘤腺苷酸琥珀酸裂解酶活性和最适pH值的影响

EFFECT OF SEVERAL IONS ON ACTIVITY AND OPTIMAL pH OF ADENYLOSUCCINATE: AMP LYASE FROM COWPEA NODULES

在含１５％（ｖ／ｖ）甘油和ｐＨ８．０的１００ｍｍｏｌ／ＬＴｒｉｃｉｎｅ缓冲液中，当离子浓度＜１５０ｍｍｏｌ／Ｌ时，Ｋ＋和Ｎａ＋离子是豇豆根瘤腺苷酸琥珀酸裂解酶（ＡＳＡＬ）的激活剂，其最适浓度约为７５ｍｍｏｌ／Ｌ，可分别提高酶活性４０％和３５％。Ｍｇ２＋离子是ＡＳＡＬ的抑制剂，能拮抗Ｋ＋和Ｎａ＋离子的激活效应。ＨＰＯ二４离子可显著降低酶活性，抑制效应与ＨＰＯ二４离子浓度呈正相关。在含１５％（ｖ／ｖ）甘油和ｐＨ６．６～８．０的１００ｍｍｏｌ／Ｌ磷酸盐缓冲液中，ＡＳＡＬ的最适ｐＨ值约为７．４，而在含１５％（ｖ／ｖ）甘油和ｐＨ７．４～８．６的Ｔｒｉｃｉｎｅ缓冲液中，ＡＳＡＬ的最适ｐＨ值约为８．２。

When their concentrations were under 150 mmol/L, K + and Na + ions were activators for adenylosuccinate: AMP lyase (ASAL) from cowpea nodules in 100 mmol/L Tricine buffer (pH 8.0) with 15% (v/v) glycerol, the optimal activator concentration was about 75 mmol/L, at which K + and Na + ions could increase ASAL activity respectively by 40% and 35%. Mg 2+ ion was not only an inhibitor for ASAL, but also an antagonist of the activation of K + and Na + ions. HPO = 4 ions sharply decreased ASAL activity. The optimal pH of ASAL was 7.4 in 100 mmol/L phosphate buffer with 15% (v/v) glycerol and 8.2 in 100 mmol/L Tricine buffer with 15% (v/v) glycerol.