Soybean lipoxygenases

Scheme 9.12 Soybean lipoxygenase (SBLO)-mediated oxygenation of fatty acid derivatives.

Grosch, W. and Laskawy, G., Co-oxidation of carotenes requires one soybean lipoxygenase isoenzyme, Biochim. Biophys. Acta, 575, 439, 1979. 

Figure 2.2 Oxidation of human LDL by lipoxygenase and exposure to copper. The oxidation of human LDL was monitored by the increase in absorbance at 234 nm after the addition of soybean lipoxygenase (LO) at t = 0 min (— and —) followed by the addition of Cu (10 fiM) at t = 90 min to one LO-treated sample (—) and the control (-). Other conditions were exactly as described in Jessup et af. (1991).

Free soybean lipoxygenase 9-Hydroperoxy-acid from y-linolenic acid Hexane-borate buffer pH 6.5(1/1) High production only in presence of anionic surfactants 23... 

Immobilized soybean lipoxygenase With carbonyldiimidazole-activated matrix termed Reacti-Gel(g) 13-Hydroperoxy-acid from linoleic acid Octane-borate buffer pH9 (5/2) No surfactant is required 24... 

We previously described [25] the function of soybean lipoxygenase-1 in a biphasic system (modified Lewis cell) composed of an aqueous phase (borate buffer) and octane. The substrate of the reaction is linoleic acid (LA) and the main product is hydro-peroxyoctadecadienoic acid (LIP). The system involves two phenomena LA transfer from the organic to the aqueous phase and lipoxygenase kinetics in the aqueous medium. 

The kinetics of soybean lipoxygenase-1 in a biphasic medium is different from the kinetics in an aqueous system [Fig. 5(a),(b)]. The kinetic curve in the two-phase system has a sigmoid shape, which is due to surface active properties of LA and HP [25]. When initial LA concentration is small in the organic phase (0-5 mM) its transfer is poor and bioconversion in the aqueous phase is slow. 

As mentioned earlier, oxidation of LDL is initiated by free radical attack at the diallylic positions of unsaturated fatty acids. For example, copper- or endothelial cell-initiated LDL oxidation resulted in a large formation of monohydroxy derivatives of linoleic and arachi-donic acids at the early stage of the reaction [175], During the reaction, the amount of these products is diminished, and monohydroxy derivatives of oleic acid appeared. Thus, monohydroxy derivatives of unsaturated acids are the major products of the oxidation of human LDL. Breuer et al. [176] measured cholesterol oxidation products (oxysterols) formed during copper- or soybean lipoxygenase-initiated LDL oxidation. They identified chlolcst-5-cnc-3(3, 4a-diol, cholest-5-ene-3(3, 4(3-diol, and cholestane-3 3, 5a, 6a-triol, which are present in human atherosclerotic plaques. 

In contrast to numerous literature data, which indicate that protein oxidation, as a rule, precedes lipid peroxidation, Parinandi et al. [66] found that the modification of proteins in rat myocardial membranes exposed to prooxidants (ferrous ion/ascorbate, cupric ion/tert-butyl-hydroperoxide, linoleic acid hydroperoxide, and soybean lipoxygenase) accompanied lipid peroxidation initiated by these prooxidant systems. 

Human 15-lipoxygenase and soybean LO-1 H/D-atom transfer from per-H vs. per-D Unoleic acid Cll to Fe-O Soybean lipoxygenase-1, WT and L546A mutant, H-atom transfer from H, D labeled linoleic acid Cll to Fe-O... 

Rickert, K.W. and Klinman, J.P. (1999). Nature of hydrogen transfer in soybean lipoxygenase 1 separation of primary and secondary isotope effects. Biochemistry 38, 12218-12228... 

Knapp, M.J., Rickert, K. and Khnman, J.P. (2002). Temperature-dependent isotope effects in soybean lipoxygenase-1 correlating hydrogen tunneling with protein dynamics. J. Am. Chem. Soc. 124, 3865-3874... 

In 1990, Triantaphylidds and coworkers reported on the preparative enzymatic synthesis of hnoleic acid (135) hydroperoxide 24a using soybean lipoxygenase-1. In this dioxygenation asymmetry is induced by the catalyst, the enzyme. The reaction was later used by Dussault and also by Baba and coworkers as key step in the preparation of more complex peroxides. The enzyme is a non-heme iron dioxygenase which catalyzes the incorporation of dioxygen into polyunsaturated fatty acids to yield E,Z conjugated diene hydroperoxides 24a-d. With this enzymatic method, the hydroperoxide 24a could... 

Instead of measuring the absorbance of the solution immediately after incubation, it is possible to determine the colored product 169 by HPLC-ELD (A.ex = 515 nm, A.fl = 553 nm). This procednre was applied for determination of MDA after oxidation of phos-phohpids catalyzed by soybean lipoxygenase . Peroxidation in the extracellular liquid of the brain cortex of rats was evaluated in vivo by microdialysis followed by reaction... 

These results indicate that the Fusarium lipoxygenase differs from the soybean lipoxygenase in various respects soybean lipoxygenase is a nonheme iron-containing dioxygenase and has a molecular weight of 102,000, optimum pH of 6.5 to 7,0 and isoelectric point of pH 5.4. The soybean enzyme is not inhibited by cyanide and catalyzes the peroxidation of linoleic acid and linolenic acid at equal rates74-76,193. ... 

Lipoxygenases, of which the enzyme from soy beans has been studied the most, also catalyze oxidation of polyunsaturated fatty acids in lipids as indicated in Eq. 21-17. Formation of the hydroperoxide product is accompanied by a shift of the double bond and conversion from cis to trans configuration. Soybean lipoxygenase is a member of a family of related lipoxygenases that are found in all eukaryotes. All... 

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