Tomato (Lycopersicon esculentum cv. Pik-Red) leaf carboxypeptidase: Identification, N-terminal sequence, stress-regulation, and specific localization in the paraveinal mesophyll vacuoles
1996
Mehta, R.A. (USDA, Agricultural Research Service, Beltsville (USA)) | Warmbardt, R.D. | Mattoo, A.K.
Wounding of tomato (Lycopersicon esculentum L.) leaves causes systemic induction of a serine-type carboxypeptidase activity. We find this activity to be present in several isoforms. Antibodies raised against the leaf carboxypeptidase inhibited the enzyme activity and the immunoprecipitates were resolved into a 69-kDa polypeptide and a doublet of 35/37-kDa proteins on SDS-PAGE. Immunoblot analysis of the leaf proteins also immunodecrorated the 69-kDa and 35/37-kDa proteins. Amino acid sequence analysis of the amino-terminus of the tomato leaf 69-kDa carboxypeptidase showed it to be similar to the barley A-chain carboxypeptidase I, sharing Ala as the N-terminus and the sequences, AlaProGln and LeuProGlyPhe. Superimposition of a chemical stress on wounding apparently lowered wound-induced carboxypeptidase activity in the leaf, suggesting that cupric ions might interact with the wound signal. Immunogold electron microscopy indicated that the leaf carboxypeptidase was specifically localized within the inclusions of vacuoles of vascular parenchyma cells. In cupric ion-treated tissues, carboxypeptidase was found redistributed to other parts of the cell, indicating that this treatment, but not wounding, causes general vacuolar membrane damage
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