Effects of polyunsaturated free fatty acids and esterified linoleoyl derivatives on oxygen consumption and C6-aldehyde formation with soybean seed homogenates

We investigated the effects of the form of fatty acid substrate with specific lipoxygenase (LOX) isozymes on O2 uptake and C6 Compound formation using a soybean seed model system at pH 6.8. In most cases lipid-dependent O2 consumption with different unsaturated free fatty acids and 18:2 derivatives was qualitatively similar to C6 aldehyde formation. LOX 1 activity was higher with arachidonic acid and linolenic acid than linoleic acid, but with LOX 1 and/or LOX 2, linoleic acid yielded the highest C6 aldehyde production. The O2 uptake and C6 aldehyde production varied considerably among the esterified firms of linoleic acid. LOX 1 was relatively more effective in the lipid-dependent O2 uptake of free fatty acids compared to esterified linoleoyl derivatives, whereas LOX 2 or 3 was relatively more effective with esterified linoleic acid than LOX 1. LOX 2 gave the highest C6 aldehyde production with all substrates except with linoleoyl coenzyme A, where LOX 1 was most effective. The C6 aldehyde formation was reduced with all substrates when LOX 3 was present in the seed homogenates