EFFECT OF SUBSTRATE POLARITY ON ACTIVITY OF SOYBEAN LIPOXYGENASE ISOENZYMES
EFFECT OF SUBSTRATE POLARITY ON ACTIVITY OF SOYBEAN LIPOXYGENASE ISOENZYMES
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DOI：
10.1007/bf02570904
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发表时间：
1977-01-01
期刊：
影响因子：
1.9
通讯作者：
AXELROD, B
中科院分区：
文献类型：
--
作者：
BILD, GS;RAMADOSS, CS;AXELROD, B
为了表征大豆的几种同工酶[EC 1.13.11.12]，对它们进行了底物极性性质的影响。一般来说，当与带电荷的底物（如阴离子形式的亚油酸或硫酸亚油酸钾）结合时，脂氧合酶-1最活跃，而脂氧合酶-2和-3更倾向于非极性底物，如未电离亚油酸、亚油酸甲酯、亚油基甲烷磺酸、10,13-壬二烯胺或醋酸亚油酯。硫酸亚油酯是脂加氧酶-1的最佳底物，是脂加氧酶-1的一种优良的易溶底物。相比之下，脂氧化酶-2和-3对该底物完全无活性。pH值为6.8时，亚油酸对脂氧合酶-2和-3的反应良好，这是由于亚油酸的pKa值比短链羧酸高得多。与亚油酸活性谱相比，脂氧合酶作用于硫酸亚油酯（在所有检查的pH值下充电）得到的pH活性谱被转移到较低的pH值。当对脂氧合酶-1进行测试时，从带电底物转变为不带电底物的效果是将Km增加一个数量级。
In order to characterize the several isoenzymes [EC 1.13.11.12] of soybeans, they were examined with respect to the effect of the polar nature of the substrate. In general, lipoxygenase-1 was most active when presented with charged substrates such as the anionic form of linoleic acid or of potassium linoleyl sulfate, whereas lipoxygenase-2 and -3 preferred nonpolar substrates such as unionized linoleic acid, methyl linoleate, linoleyl methane sulfonate, 10,13-nonadecadieneamine, or linoleyl acetate. Linoleyl sulfate, which was advanced as an excellent readily soluble substrate for lipoxygenase, was indeed the best substrate found for lipoxygenase-1. Lipoxygenase-2 and -3 were, by contrast, totally inactive against this substrate. The favorable response of linoleic acid to lipoxygenase-2 and -3 at pH 6.8 was ascribed to the anomalously high pKa value of linoleic acid compared to that of short chain carboxylic acids. The pH-activity profile obtained with lipoxygenase acting on linoleyl sulfate (which was charged at all pH values examined) was shifted to lower pH values compared to the linoleic acid activity profile. The effect of changing from the charged to the uncharged substrate, when tested against lipoxygenase-1, was to increase the Km by an order of magnitude.