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KMID : 0613820020120060752
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Journal of Life Science
2002 Volume.12 No. 6 p.752 ~ p.758
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Properties and Thermostability of Gelatin-degrading Proteinases in the Fruit of Actinidia chinensis (Kiwifruit)
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Oh Soon-Ja
Kim Seong-Cheol
Koh Seok-Chan
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Abstract
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This study was investigated on properties and thermostability of gelatin-degrading proteinases in the fruit of Actinidia chinensis (kiwifruit) for the industrial application. Three gelatin-degrading proteinases (PⅠ, PⅡ and PⅢ) were detected from the pulp of fruits. The molecular weights of these proteinases, PⅠ, PⅡ and PⅢ, were approximately 220 kD, 51 kD, and 26 kD respectively, on the basis of gelatin-containing SDS-PAGE. The optimum pH of these proteinases ranged from 2.0 to 5.0 with a maximal activity at pH 4.0. These proteinases had a high sensitivity to E-64 and iodoacetate which are cysteine protease inhibitors, and required DTT, cysteine, and β-mercaptoethanol for their activities which are stimulators for cysteine proteases. These results indicate that these proteinases are cysteine proteinases and the proteinase PⅢ is actinidin (EC 3.4.22.14), based on the molecular weight and/or susceptibility against proteinase inhibitors. These proteinases were strongly activated by Ca²+, Mg²+ and Mn²+, whereas strongly inhibited by Zn²+ and Hg²+. However, these proteinases have slightly different susceptibility against other cations (Co²+, Cu²+, Al³+, Fe³+). The temperature stability of proteinase PⅢ was more stable than proteinases PⅠ and PⅡ. Moreover, proteinase PⅢ remained stable below 50℃ for 48hr, showing the residual activity above 75% of the enzyme activity.
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KEYWORD
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kiwifruit (Actinidia chinensis), gelatin-degrading proteinases, cysteine proteinases, actinidin
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