Oxygenation of unsaturated fatty acids by soybean lipoxygenase
WL Smith, WEM Lands - Journal of biological chemistry, 1972 - Elsevier
WL Smith, WEM Lands
Journal of biological chemistry, 1972•ElsevierLipoxygenase 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 (κ 2)
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 …
destruction is first order with respect to enzyme. The rate constant for this inactivation (κ 2)
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 …
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.
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