• Journal of the Korean Society of Food Science and Nutrition
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• v.27 no.5
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• pp.808-812
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• 1998

Melania snail(Semisulcopira bensoni) is used as ingredient in Korean traditional soup and nutritional foods. Generally, lipoxygenase in several food products may produce off-flavors during their processing and storage. Therefore, the inactivation of lipoxygenase is required to make the better extracts from Melania sanil. Also, the quality on freshness of Melania snail may be evaluated by lipoxygenase activity. The lipoxygenae activity was the highest at 40~60% saturation among several concentrations in salting-ouot saturated solution of ammonium sulfate. The partial purification of lipoxygenase was successfully obtained by Sephacryl S-200 gel chromatography. The first peak among three peaks for protein determination showed the highest activity of lipoxygenase in 13~16 fractions among 100 fractions. The highest peak of lipoxygenase activity by ion exchange chromatography was shown at 0.1M NaCl. In the purification step, the specific activity was 20.8U/mg and activity yield was 19.8%. The optimum pH and temperature were pH6.0~8.0 and 3$0^{\circ}C$, respectively. Molecular weight of the lipoxygenase was estimated about 35kDa by SDS-PAGE.

• Journal of the Korean Society of Food Science and Nutrition
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• v.22 no.6
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• pp.833-838
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• 1993

A strain of Penicillium sp. extracellularly produced an inhibitory substance for lipoxygenase. These purification procedures were followed : ethanol treatment, chromatographies on Dowex 50W, Sephadex G-25, silica gel column and HPLC. The inhibitor was stable in pH range from 3.0 to 5.0 at $25^{\circ}C$, and a treatment at 10$0^{\circ}C$ for 2 hours didn't diminish its original activity. The purified inhibitor was charred at temperature near 22$0^{\circ}C$~23$0^{\circ}C$ and decomposed. Molecular weight of the inhibitor was estimated to be approximately 270 by Sephadex G-25 column chromatography. The inhibitor rapidly formed EI complex with lipoxygenase and inhibited enzyme activity.

• BMB Reports
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• v.33 no.2
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• pp.172-178
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• 2000

The lipoxygenase was purified 35 fold to homogeneity from the Korean red potato by an ammonium sulfate precipitation and DEAE-cellulose column chromatography. The simple purification method is useful for the preparation of pure lipoxygenase. The molecular weight of the enzyme was estimated to be 38,000 by SDS-polyacrylamide gel electrophoreses and Sepharose 6B column chromatography. The purified enzyme with 2 M $(NH_4)_2SO_4$ in a potassium phosphate buffer, pH 7.0, was very stable for 5 months at $-20^{\circ}C$. Because the purified lipoxygenase is very stable, it could be useful for the screening of a lipoxygenase inhibitor. The optimal pH and temperature for lipoxygenase purified from the red potato were found to be pH 9.0. and $30^{\circ}C$, respectively. The Km and Vmax values for linoleic acid of the lipoxygenase purified from the red potato were $48\;{\mu}M$ and $0.03\;{\mu}M$ per minute per milligram of protein, respectively. The enzyme was insensitive to the metal chelating agents tested (2 mM KCN, 1 and 10mM EDTA, and 1 mM $NaN_3$), but was inhibited by several divalent cations, such as $Cu^{++}$, $Co^{++}$ and $Ni^{++}$. The essential amino acids that were involved in the catalytic mechanism of the 5-lipoxygenase from the Korean red potato were determined by chemical modification studies. The catalytic activity of lipoxygenase from the red potato was seriously reduced after treatment with a diethylpyrocarbonate (DEPC) modifying histidine residue and Woodward's reagent (WRK) modifying aspartic/glutamic acid. The inactivation reaction of DEPC (WRK) processed in the form of pseudo-first-order kinetics. The double-logarithmic plot of the observed pseudo-first-order rate constant against the modifier concentration yielded a reaction order 2, indicating that two histidine residues (carboxylic acids) were essential for the lipoxygenase activity from the red potato. The linoleic acid protected the enzyme against inactivation by DEPC(WRK), revealing that histidine and carboxylic amino acids residues were present at the substrate binding site of the enzyme molecules.

• Korean Journal of Food Science and Technology
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• v.19 no.4
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• pp.295-299
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• 1987

Mungbean Lipoxygenase was purified by ammonium sulfate fractionation, DEAE-sephacel column chromatography and sephadex G-200 gel filtration. The specific activity of pfurified enzyme was 23.4U/mg protein and the yield was 12%. Optimal activity of the enzyme was observed at pH 8.4 and the enzyme had Km value of 0.25mM for linoleic acid. The enzyme was stable in the range of pH 5.0-7.0 and at temperature below $50^{\circ}C$. The enzyme activity was inhibited by antioxidants such as nordihydroguiaretic arid and chelating agents.

• Korean Journal of Food Science and Technology
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• v.19 no.5
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• pp.397-402
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• 1987

Two lipoxygenases (F-I and F-II) were purified from potato tubers by ammonium sulfate fractionation and ion-exchange column chromatographies. The purified isoenzymes were apparently homogeneous on polyacrylamide gel electrophoresis. Both enzymes showed a similar optimum pH of 5.5-6.0. From thermal inactivation experiments with the purified enzymes in the range of 50 to $65^{\circ}C$, D-values of 13.3 min and 4.3 min at $65^{\circ}C$, and z-values of $11.8^{\circ}C\;and\;10.3^{\circ}C$ were obtained respectively for F-I and F-II. By applying absolute reaction rate equation, thermodynamic parameters wire also determined for the activation part of the inactivation process.