The peroxidase/oxidase activity of soybean lipoxygenase--I. Triplet excited carbonyls from the reaction with isobutanal and the effect of glutathione.
Soybean lipoxygenase shows a secondary peroxidase/oxidase activity: The aerobic reaction with isobutanal, enhanced by hydrogen peroxide as a cosubstrate, yields acetone, exhibits chemiluminescence and consumes oxygen (phi cl = 1.3 x 10(-9) photons/O2 molecule consumed). 9,10-Dibromoanthracene-2-sulfonate increases the photoemission (kET tau 0 = 2 x 10(4) M-1; phi cl = 0.9 x 10(-7) photons/O2), whereas it is diminished by sorbate, tryptophan, 2-methyl-1,4-naphthoquinone, glutathione, and superoxide dismutase. In the presence of hydrogen peroxide the lipoxygenase reaction with glutathione yields yet another excited state. From the well-known reactions promoted by horseradish-peroxidase, these features are concluded to indicate the novel activity of soybean lipoxygenase. With isobutanal as a substrate lipoxygenase acts as an oxidase and as a peroxidase. The mechanism suggested leads to photoemissive triplet excited acetone as expected from the cleavage of an intermediate dioxetane.
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D000447:Aldehydes; D005978:Glutathione; D008084:Lipoxygenase / Q000378:metabolism*; D049449:Luminescence; D013025:Glycine max / Q000201:enzymology*
D000447:Aldehydes; C017439:isobutyraldehyde; D008084:Lipoxygenase; D005978:Glutathione