Photolysis of "purple" lipoxygenase: implications for the structure of the chromophore.
Treatment of soybean lipoxygenase isozyme 1 with its substrates, linoleic acid and oxygen, or product, 13(S)-hydroperoxy-9,11(Z,E)-octadecadienoic acid (13-HPOD), leads to the appearance of a purple color. Although the structure of the chromophore has not been determined, we present strong evidence that it is an Fe(3+)-OOR complex between the enzyme and 13-HPOD. Irradiation of frozen purple solutions of lipoxygenase causes the reversible production of a radical, shown by the effects of 2H and 17O enrichment on its EPR spectrum to be derived from 13-HPOD. The action spectrum of the photolysis reaction corresponds to the visible spectrum of the purple species, strongly implying that the purple chromophore contains 13-HPOD (or a product thereof) as part of its structure. Concomitant with the production of this radical there is a decrease in the intensity of an EPR signal corresponding to enzyme-bound Fe3+ and characteristic of the purple species. Taken together, these observations support the suggestion that the purple species is a complex between ferric lipoxygenase and 13-HPOD, likely the ferric peroxide.
Nelson
M J
MJ
Central Research and Development, DuPont, Wilmington, Delaware 19880-0328, USA.
Chase
D B
DB
Seitz
S P
SP
D002863:Chromogenic Compounds / Q000737:chemistry*; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000737:chemistry* / Q000378:metabolism; D008054:Lipid Peroxides; D008084:Lipoxygenase / Q000737:chemistry* / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010782:Photolysis; D013025:Glycine max / Q000201:enzymology; D013057:Spectrum Analysis
D002863:Chromogenic Compounds; D008041:Linoleic Acids; D008054:Lipid Peroxides; C038649:13-hydroperoxy-9,11-octadecadienoic acid; D019787:Linoleic Acid; D008084:Lipoxygenase; D010100:Oxygen