Abstract
Kiwi fruit extract showed proteolytic activity at pH 3, 6 and 9 when casein was used as a substrate, and each activity showed different heat-stability. These results suggested that kiwi fruit contains proteases which have various pH optima. It was observed by SDS-PAGE that kiwi protease cleaves specifically the telopeptide region containing intramolecular cross-links in collagen molecules at pH 3. Proteases with various pH optima were not separated by gelatin-PAGE. The molecular weight of the proteases is estimated to be 22, 000 by SDS-PAGE. By using an Ampholine plate, their isoelectric point was shown to be pH 3.5 or below.
