Chymotrypsin inhibitor from potatoes: interaction with target enzymes |
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Authors: | Jerry Lee Eddy Judith E. Derr G.Michael Hass |
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Affiliation: | Department of Bacteriology and Biochemistry University of Idaho, Moscow, ID 83843, U.S.A. |
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Abstract: | The interactions of chymotrypsin, subtilisin and trypsin with a low MW proteinase inhibitor from potatoes were investigated. The Ki value calculated for the binding of inhibitor to chymotrypsin was 1.6 ± 0.9 × 10?10M, while the second-order rate constant for association was 6 × 105 M?1/sec. Although binding was not observed to chymotrypsin which had been treated with diisopropyl fluorophosphate or with l-tosylamide-2-phenylethyl chloromethyl ketone, the 3-methylhistidine-57 derivative bound inhibitor with a Ki value of 9.6 × 10?9 M. The inhibitor also exhibited a tight association with subtilisin (Ki < 4 × 10?9 M). In contrast, little inhibition of trypsin was observed, and this was believed to be due to low levels of a contaminant in our preparations. No evidence for reactive site cleavage was observed after incubation of the inhibitor with catalytic amounts of chymotrypsin or subtilisin at acid pH. |
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Keywords: | Solanaceae potato protease inhibitor protease chymotrypsin subtilisin |
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