Isolation and characterization of a protease inhibitor from spinach leaves |
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Authors: | Shinobu Satoh Emi Satoh Tsuneo Watanabe Tadashi Fujii |
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Institution: | 1. Institute of Biological Sciences, University of Tsukuba, Sakura-mura, Ibaraki 305, Japan;2. National Institute for Environmental Studies, Yatabe-cho, Ibaraki 305, Japan |
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Abstract: | An acid-stable and heat-labile proteinous protease inhibitor which was found in spinach leaves but not in seeds was isolated by sequential chromatography and preparative isoelectric focusing. The isoelectric point of this inhibitor was 4.5. The inhibitor had a Mr of ca 18 000 and was rich in aspartic acid and glycine; it had 4 half-cystine, 2 tryptophan and no methionine residues. Its extinction coefficient (E|cm%) was 13.7 at 280 nm. The inhibition was competitive and the dissociation constant was 3.32 × 10?13 M. The inhibitor was specific to serine proteases and strongly inhibited trypsin and weakly inhibited α-chymotrypsin and kallikrein. |
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Keywords: | Chenopodiaceae spinach leaf protease inhibitor serine protease trypsin |
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