Isolation and properties of carboxypeptidase from leaves of wounded tomato plants |
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Authors: | M Walker-Simmons CA Ryan |
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Institution: | Department of Agricultural Chemistry and Program in Biochemistry and Biophysics, Washington State University, Pullman, WA 99164, U.S.A. |
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Abstract: | A carboxypeptidase was purified to homogeneity from upper, unwounded leaves of tomato plants in which carboxypeptidase activity had been induced to increase over three-fold by severely wounding the lower leaves. The carboxypeptidase was purified by ammonium sulfate precipitation, affinity chromatography, and finally by gel permeation chromatography. Electrophoresis at pH 4.3 and isoelectric focusing showed only a single band. The isoelectric point was 5.2 and the MW 105 000. Tomato carboxypeptidase possessed both peptidase and esterase activities and it sequentially hydrolysed amino acids from the carboxyl-terminal end of insulin chain B. It was optimally active at pH 6–7 on peptidase substrates, and at pH 8 on esterase substrates. The enzyme was inhibited by diisopropylfluorophosphate and incorporated 1 mol of DFP-3H]. per mol of enzyme. Both peptidase and esterase activities were strongly inhibited by HgCl2 but not by p-hydroxymercuribenzoate or iodoacetamide. Carboxypeptidase inhibitor from potatoes did not inhibit the enzyme. |
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Keywords: | Solanaceae tomato wound-induced leaves carboxypeptidase exopeptidase DFP diisoprophyl fluorophosphate DIP diisoprophyl phosphoryl EDTA ethylenediaminetetraacetic acid IAAm idodoacetamide SDS sodium dodecyl sulfate Tris tris(hydroxymethyl)-aminomethane To whom inquiries should be sent |
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