TOMATO (LYCOPERSICON-ESCULENTUM CV. PIK-RED) LEAF CARBOXYPEPTIDASE - IDENTIFICATION, N-TERMINAL SEQUENCE, STRESS-REGULATION, AND SPECIFIC LOCALIZATION IN THE PARAVENOUS MESOPHYLL VACUOLES

Wounding of tomato (Lycopersicon esculentum L.) leaves causes systemic induction of a serine-type carboxypeptidase activity. We find this ac tivity to be present in several isoforms. Antibodies raised against th e leaf carboxypeptidase inhibited the enzyme activity and the immunopr ecipitates 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 immunodecorated the 69-kDa and 35/37-kDa proteins. Amino acid se quence analysis of the amino-terminus of the tomato leaf 69-kDa carbox ypeptidase showed it to be similar to the barley A-chain carboxypeptid ase I [Sorenson et al. (1986) Carlsberg Res. Commun. 51: 475], sharing Ala as the N-terminus and the sequences, AlaProGln and LeuProGlyPhe. Superimposition of a chemical stress (copper treatment) on wounding ap parently lowered wound-induced carboxypeptidase activity in the leaf, suggesting that cupric ions might interact with the wound signal. Immu nogold electron microscopy indicated that the leaf carboxypeptidase wa s 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.