• Journal of the Korean Chemical Society
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• v.50 no.5
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• pp.362-368
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• 2006

SH group modifying chemicals were used to characterize the eight cysteine residues of cabbage PLD. 5,5-dithiobis(2-nitrobenzoate)(DTNB) was used to titrate the SH group of cysteine residues . Based on the optical density at 412nm due to the reduced DTNB, 4 SH groups are found to be present in a native PLD while 8 SH groups in the denatured PLD whose tertiary structure was perturbed by 8M urea. The results imply that among the 8 cysteine residues of PLD, the half(4) are exposed on the surface whereas the other half are present at the interior of the enzyme tertiary structure. The PLD was inactivated by SH modifying reagents such as p-chloromercuribenzoate(PCMB), iodoacetate, iodoacetamide, and N-ethylmaleimide. At the addition of dithiothreitol(DTT) only the PCMB inhibited PLD activity was recovered reversibly. The micro-environment of the exposed SH group of cysteine residues was examined with various disulfide compounds with different functional groups and we found that anionic or neutral disulfides appear to be more effective than the positively charged cystamine for inactivating the PLD activity. The effect of redox state of cysteine residues on the PLD activity was further explored with H2O2. The oxidation of SH groups by H2O2 inhibited the PLD activity more than 70%, which was mostly recovered by DTT. From these results, we could confirm chemically that all the cysteine residues of PLD are present as in their reduced SH forms and the 4 SH groups exposed on the surface of the enzyme may play important roles in the regulation of PLD activity.

• The Korean Journal of Physiology and Pharmacology
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• v.3 no.6
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• pp.631-640
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• 1999

The present study investigated the stimulatory effects of iron (or ascorbate) on cyclosporine-induced kidney mitochondrial damage. Damaging effect of $50\;{\mu}M$ cyclosporine plus $20\;{\mu}M\;Fe^{2+}$ on mitochondrial lipids and proteins of rat kidney and hyaluronic acid was greater than the summation of oxidizing action of each compound alone, except sulfhydryl oxidation. Cyclosporine and $100\;{\mu}M$ ascorbate showed an enhanced damaging effect on lipids but not on proteins. The peroxidative action of cyclosporine on lipids was enhanced with increasing concentrations of $Fe^{2+}.$ Ferric ion $(20\;{\mu}M)$ also interacted with cyclosporine to stimulate lipid peroxidation. Damaging action of cyclosporine on mitochondrial lipids was enhanced by ascorbate $(100\;{\mu}M\;and\;1\;mM)$. Iron chelators, DTPA and EDTA, attenuated carbonyl formation induced by cyclosporine plus ascorbate. Cyclosporine $(100\;{\mu}M)$ and $50\;{\mu}M\;Fe^{2+}$ $(or\;100\;{\mu}M\;ascorbate)$ synergistically stimulated degradation of $2-{\alpha}$ deoxyribose. Cyclosporine $(1\;to\;100\;{\mu}M)$ reduced ferric ion in a dose dependent manner, which is much less than ascorbate action. Addition of $Fe^{2+}$ caused a change in absorbance spectrum of cyclosporine in $230{\sim}350$ nm of wavelengths. The results show that cyclosporine plus iron (or ascorbate) exerts an enhanced damaging effect on kidney mitochondria. Iron and ascorbate appear to promote the nephrotoxicity induced by cyclosporine.

• The Korean Journal of Pharmacology
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• v.21 no.2
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• pp.79-89
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• 1985

Mechanism of calcium transport inhibition of cardiac sarcoplasmic reticulum (SR) by oxygen free radicals was examined. Effects of oxygen free radicals generated by xanthine/xanthine oxidase (X/XO) system on isolated porcine ventricle SR were studied with respect to its calcium binding, lipid peroxidation, SH-group content and alteration of membrane protein components. The results are as follows. 1) Calcium binding of isolated SR was markedly inhibited by X/XO. 2) During the incubation of sarcoplasmic reticulum with xanthine/xanthine oxidase, there were marked inclose in lipid peroxidation and reduction of SH-group content. 3) An antioxidant, p-phenylenediamine effectively prevented the lipid peroxidation but partially prevented the calcium binding inhibition of X/XO treated SR. 4) The reduction of SH-group content of SR treated with X/XO was partially prevented by p-phenylendiamine. 5) When modifying SH-group of SR by treatment with DTNB, the inhibition of calcium binding activity was partially prevented. 6) On gel-permeation chromatography of X/XO-treated sarcoplasmic reticulum, there was an increase of small molecular weight products, probably protein degradation products. 7) Semicarbazide, which prevents the cross-linking reaction of protein components, did not affect the calcium binding inhibition of X/XO-treated SR. From these results, it is suggested that the inhibition of calcium binding of SR by oxygen free radicals results from the consequence of multiple changes of SR components, which are lipid peroxidation, SH-group oxidation and degradation of protein components.

• Food Science of Animal Resources
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• v.39 no.2
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• pp.240-254
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• 2019

This study investigated the effect of storage state (chilled state on sous-vide, CS; frozen state without thawing on sous-vide, FS; and frozen/thawed states on sous-vide, TS) and sous-vide cooking temperature ($65^{\circ}C$ and $72^{\circ}C$) on the longissimus dorsi muscle quality of pork. FS showed a higher moisture content than that of CS and TS (p<0.001), whereas both FS and CS showed higher expressible moisture loss than that of TS (p<0.001). FS showed a lower cooking loss (p<0.001) than that of CS and TS. FS and TS exhibited significantly higher lipid oxidation than that of CS. Carbonyl and sulfhydryl content were not significantly affected by the storage treatment. FS and TS exhibited lower shear force than that of CS (p<0.001). FS and TS showed higher springiness than that of CS (p<0.001), FS exhibited lower gumminess than that of CS and TS (p<0.01). Sous-vide treatment at $65^{\circ}C$ exhibited significantly higher moisture content and lower expressible moisture loss, cooking loss, and total and sarcoplasmic protein than those at $72^{\circ}C$. Shear force and springiness of $65^{\circ}C$-treated groups were lower than those of $72^{\circ}C$-treated groups (p<0.01). Cooking temperature significantly influenced overall acceptability, whereas the storage state did not affect the overall acceptability. These results indicated that meat quality might be improved upon cooking from the frozen or frozen/thawed state using sous-vide when compared with traditional processing.