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  • Title: In vitro oxygenation of soybean biomembranes by lipoxygenase-2.
    Author: Maccarrone M, van Aarle PG, Veldink GA, Vliegenthart JF.
    Journal: Biochim Biophys Acta; 1994 Feb 23; 1190(1):164-9. PubMed ID: 8110809.
    Abstract:
    The ability of soybean lipoxygenases-1 and -2 to oxygenate biomembranes isolated from soybean seedlings has been investigated. Constituents of the lipid bilayer were analyzed by means of reversed phase and chiral phase high performance liquid chromatography, gas chromatography/mass spectrometry, high performance thin layer chromatography and uv spectroscopy. Evidence is presented that soybean lipoxygenase-2, at variance with the type-1 enzyme, oxygenates the esterified unsaturated fatty acid moieties in biomembranes, whereas membrane-embedded free unsaturated fatty acid moieties were not a suitable substrate for either isoenzyme. The oxygenation products derived from the biomembranes were the 9- and 13-hydroperoxides of linoleic acid residues, in a molar ratio of 1.0 to 1.7, and the 9- and 13-hydroperoxides of alpha-linolenic acid residues, in a molar ratio of 1.0 to 0.1. The R/S ratios of 13-hydroperoxy-9Z,11E-octadecadienoic acid and 9-hydroperoxy-10E,12Z,15Z-octadecatrienoic acid were found to be 0.5 and 25.0, respectively. These stereospecificity values were much higher than those of hydroperoxides isolated after incubation of lipoxygenase-2 with non-membraneous fatty acids or their methyl esters. The hydroperoxy fatty acids produced were distributed in neutral lipids and phospholipids isolated from soybean membranes, the former being oxidized to a larger extent. Furthermore, both intracellular and plasma membranes were substrates for the enzymic oxygenation, with a preference for those of chloroplasts followed by those of Golgi apparatus, endoplasmic reticulum, plasma membrane and mitochondria. These data point towards a different action of the two lipoxygenases in soybean cells. We suggest that the type-2 enzyme plays a role in the in vivo remodelling of biomembranes. The physiological relevance of these findings is discussed.
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