Co-oxidation of [beta]-carotene by soybean lipoxygenase

Abstract

Isolation and purification of the enzyme 75 Linoleate and 3-carotene-oxidizing activities 81 Linoleic Acid Hydroperoxide (LOOK) 84 Preparation and isolation 84 Characterization 89 Enzymatic and Nonenzymatic Oxidation of B-Carotene 92 3-Carotene oxidation by the linoleatelipoxygenase system 103 3-Carotene oxidation by the LOOH-lipoxygenase system 111 Autoxidative bleaching of g-carotene 117 Mass spectrometry of some carotenoids 130 Carotenoids-U-C^^ from Chlorella pyrenoidosa 136 Biosynthesis , 136 Enzymatic degradation of lutein-U-C 138 Some Parameters of 3-Carotene Bleaching by Lipoxygenase 140 157 Kinetics of 3-carotene oxidation 160 LOOK and 3-Carotene Bleaching by Lipoxygenase 164 Effect of LOOH on the rate of 3-carotene bleaching 164 Uptake of molecular oxygen by the LOOHlipoxygenase system 170 The Nature of the Co-oxidation Reaction 176 Inferences from inhibition studies 176 iv Page Conclusions from the nature of the reaction products 177 Proposed co-oxidation pathway 180 Nature of the activated reactive inter mediate

β-Carotene and Capsanthin Co-oxidation by Lipoxygenase. Kinetic and Thermodynamic Aspects of the Reaction

“…Holden (1965) blanched chloroplastic pigments with soybean extract and found that lipoxygenase promoted more degradation in chlorophyll compounds than in carotenoids, and Hildebrand and Hymowitz (1982) confirmed these results. Ikediobi and Snyder (1977) specifically studied the capacity of lipoxygenases in the blanching of carotenoids, and found that the mixture of LOX-2 and LOX-3 had a greater blanching effect on β-carotene than the alkaline lipoxygenase alone (LOX-1). Reynolds and Klein (1982) found low carotenoid blanching capability in LOX-1 from soybeans and peas.…”

A proposed mechanism for the inhibition of soybean lipoxygenase by β‐carotene

“…It is thought that β‐carotene, at concentrations capable of preventing the formation of linoleic acid hydroperoxides, reacts with intermediate radicals formed during LOX‐mediated linoleic acid oxidation and does not transform into its oxidized forms that do not absorb at 460 nm. β‐Carotene oxidation during LOX‐mediated linoleic acid oxidation has been reported in various studies for the enzymes extracted from potato,30 pea,31–33 soybean,23, 34 wheat,28, 35 olive36 and pepper 37, 38…”

“…This effect is also known as co‐oxidation 8. According to some reporters, this enzymatic co‐oxidation of pigments can be used as a system for indirect measurement of LOX activity, the rates of pigment destruction correlating with the amount of enzyme 23…”