1-AMINOCYCLOPROPANE-1-CARBOXYLATE SYNTHASE - ARE THERE CHARGE AND SIZE VARIANTS IN TOMATO

Several techniques of electrofocusing have been used to determine whether 1-aminocyclopropane-1- carboxylate (ACC) synthase isolated from wounded tomato pericarp tissue exists in different isoforms, each with its characteristic isoelectric point (pI).The pI of the native enzyme was found to be 6.0 ± 0.2.When radiolabeled, denatured ACC synthase was electrofocused by non-equilibrium pH gradient electrophoresis (NEpHGE), the enzyme separated into four discernible spots which, upon reaching equilibrium, ranged in pI from 6.6 to 6.9.Immunopurified ACC synthase from four tomato cultivars (Duke, Cornell, Mountain Pride and Pik Red) migrated in each case as a 50 kDa protein on sodium dodecyl sulfate polyacrylamide gels (SDS-PAGE).We propose that native ACC synthase in extracts of tomato pericarp tissue exists in one single size and that the charge heterogeneities observed upon electrofocusing of denatured enzyme result from modifications of pre-existing protein. © 1990, Gustav Fischer Verlag, Stuttgart. All rights reserved.