ACIDIFIED PHENOL ALTERS TOMATO CELL-WALL PECTIN SOLUBILITY AND CALCIUM CONTENT

The inactivation of cell wall enzymes is often accomplished by exposing the wall to phenol-acetic acid-water (PAW; 2:1:1, w/v/v) during isolation. We investigated the influence of this solvent on the solubility characteristics of pectin and calcium in cell wall derived from tomato pericarp tissue. When placed in 50 mM NaOAc at pH 6.5, cell wall from ripe fruit which had not received a PAW treatment released from 25 to 30-mu-g galacturonic acid equivalents (mg cell wall)-1. The inclusion of the chelator cyclohexane-trans-1,2-diamine tetraacetic acid (CDTA) increased recoveries from non-PAW treated wall to nearly 160-mu-g mg-1. In contrast, PAW-treated wall from ripe fruit when placed in buffer without chelator released 170-mu-g mg-1; recoveries were not enhanced in the presence of chelator. Pectin solubility was also enhanced in PAW-treated wall from mature-green pericarp. PAW-treated wall exhibited a 35-50% reduction in calcium and showed greatly enhanced susceptibility to hydrolysis by polygalacturonase. Buffered phenol was examined as a possible alternative to PAW. Cell wall exposed to Tris-buffered phenol (pH 7.0) were enzymically inactive, showed no reduction in calcium and exhibited chelator-dependent pectin solubilization.