Oxygenation of unsaturated fatty acids by soybean lipoxygenase.
Oxygenation of unsaturated fatty acids by soybean lipoxygenase.
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大豆脂氧合酶对不饱和脂肪酸的氧化。
DOI：
10.1016/s0021-9258(19)45612-3
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发表时间：
1972
期刊：
影响因子：
--
通讯作者：
W. Lands
中科院分区：
文献类型：
--
作者：
W. Smith;W. Lands
脂肪氧合酶在脂肪酸底物的氧化过程中催化自身的破坏。对酶的破坏是第一级的。这种失活的速率常数(κ2)对于每种脂肪酸底物都有一个特征值。相应地，不饱和度较高的酸的值更大。在有产物存在的情况下，酶在脂肪酸和氧气两种底物作用下的失活速度都是单独作用时的10倍。我们已经证实，脂肪氧合酶对脂肪酸的氧化有一个动力学滞后期，可以通过添加产物过氧化氢来消除。产物过氧化氢在整个自催化反应中起着至关重要的作用。我们进一步证明，由于多烯酸底物对酶的抑制，延迟期可能会延长。以前报道的谷胱甘肽存在下GSH过氧化物酶抑制脂氧合酶的作用似乎是由于过氧化氢产物的去除。这些发现和其他发现可以用动力学模型来解释，在该模型中，产物和脂肪酸底物都存在不同的作用，允许产物仅结合在产物部位，而脂肪酸底物可以结合在任何一个部位。
Lipoxygenase catalyzes its own destruction during oxygenation of fatty acid substrates. The destruction is first order with respect to enzyme. The rate constant for this inactivation (κ2) has a characteristic value for each fatty acid substrate. The values are greater for acids having correspondingly higher degrees of unsaturation. In the presence of product, the enzyme loses activity 10 times faster with both substrates, fatty acid and oxygen, present than with either alone.We have confirmed that oxygenation of fatty acids by lipoxygenase occurs with a kinetic lag period which can be abolished by adding product hydroperoxides. Product hydroperoxides play an essential role in the over-all autocatalytic reaction. We have further shown that the lag period may be extended as a result of inhibition of the enzyme by polyenoic acid substrates. The previously reported inhibition of lipoxygenase by GSH peroxidase in the presence of glutathione appears to be due to the removal of the hydroperoxide product.These findings as well as those of others may be accommodated by a kinetic model in which distinct roles exist for both the product and the fatty acid substrate in a manner allowing product binding only at the product site whereas fatty acid substrates may bind at either site.