Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1986: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1985: ¥1,400,000 (Direct Cost: ¥1,400,000)
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Research Abstract |
In lipid oxidation during cold storage of fish, the authors found that TBA/kg skin of fatty fish was always higher than that of lean fish, whereas TBA/10g lipid in the skin of lean fish was higher than that of fatty fish. It was probable that some prooxidant caused high TBA/10g lipid in the skin of lean fish. The enzyme, lipoxygenase, was extracted from the skin of Striped pigfish and was purified by gel filtration with Sephadex G-100 followed by ion exchange chromatography on DEAE Sephadex A-50. Hydroperoxide produced by the lipoxygenase from fish skin were observed in thin-layer chromatography to coincide in RF value with that produced by soybean lipoxigenase. Optimal pH for the enzyme was 6. At pH 7 the enzyme was stable. Most of the enzyme activity disappeared by heating for 20 min at 100゜C. The enzyme showed higher specificity for linoleic acid. The michaelis constant for linoleic acid was determined to be 6.81 x <10^(-3)> M. The molecular weight was estimated 174,000 by Sephadex G-100 gel filtration. The extracts from the skin of Striped pigfish (I), from the dark muscle of Striped pigfish (II) and from the skin of Pacific mackerel (III) were applied to a Sephadex G-100 column, respectively. (I) was separated into three fractions (Frs.A, B and C) with lipoxygenase activity. But, (II) and (III) presented only each one fraction which accelerated lipid oxidation and corresponded to Fr.C in (I). Fraction A containing lipoxygenase was found only in (I) which was from the skin of lean fish, but not in (III) which was of fatty fish. The molecular weights of Frs.B and C were about 70,000 and 17,000 which were nearly equal to those of hemoglobin and myoglobin, respectively. From these results, the authors concluded that high TBA/10g lipid in the skin from lean fish was caused by this enzyme.
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