Abstract
The activity of polygalacturonase (PG) has been detected in ripe McIntosh apples (Malus domestica Borkh. cv McIntosh) both by enzyme activity measurement and immunoblotting using an anti-tomato-PG antibody preparation. PG activity increased during fruit ripening and remained steady, or decreased slightly, after 5 months of controlled atmospheric storage. The enzyme had a relative molecular weight of 45,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 56,000 to 61,000 when determined by gel filtration. Viscosity and reducing end group measurements with a commercial pectin preparation showed that the enzyme is endo acting. In RNA and DNA blot hybridization experiments, a full-length tomato PG cDNA hybridized with the apple RNA and DNA, showing the identity of genes encoding the activity of the enzyme in tomato and apple.