Co-oxidation of beta-carotene catalyzed by soybean and recombinant pea lipoxygenases.
A number of products including apocarotenal, epoxycarotenal, apocarotenone, and epoxycarotenone generated by lipoxygenase (LOX) catalyzed co-oxidation of beta-carotene have been tentatively identified through the use of GC/MS and HPLC combined with photodiode array detection. Because of the large number of high molecular weight products detected and their probable chemical structures, a co-oxidation mechanism is proposed that involves random attack along the alkene chain of the carotenoid by a LOX-generated linoleoylperoxyl radical. It is suggested that a direct release from the enzyme of the radical, which initiates the co-oxidation of beta-carotene, is greater for pea LOX-3 than for pea LOX-2 or soybean LOX-1. It is proposed that further products may be formed by free radical propagated reactions and that the formation of 1,10- and 1,14-dicarbonyl compounds may arise by secondary oxidation of the primary products.
Wu
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Z
Biocatalysts Ltd., Pontypridd, Mid-Glamorgan CF37 5UT, United Kingdom.
Robinson
D S
DS
Hughes
R K
RK
Casey
R
R
Hardy
D
D
West
S I
SI
D000975:Antioxidants / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D008084:Lipoxygenase / Q000378:metabolism*; D010084:Oxidation-Reduction; D018532:Pisum sativum / Q000201:enzymology*; D011994:Recombinant Proteins / Q000378:metabolism; D013025:Glycine max / Q000201:enzymology*; D019207:beta Carotene / Q000378:metabolism*
D000975:Antioxidants; D011994:Recombinant Proteins; D019207:beta Carotene; D008084:Lipoxygenase