Changes in Firmness of Strawberry Fruit During Growth and Partial Purification of its Polygalacturonase

The correlation between firmness change in strawberry fruit (Fragaria ananassa, Duch. CV. Toyonoka) and molecular weight distribution of water soluble polyuronides (WSP) during softening was investigated. Lower-molecular-size polyuronides increased slightly with fruit development. A low level of polygalacturonase (PG) activity was found in this fruit throughout the developing stage, and it was shown to consist of three enzymes (PG1,2, and 3) that could be separated by cation-exchange chromatography. PG1 released a small amount of oligomers in addition to galacturonic acid (GA). On the other hand, PG2 released only GA, indicating an exo-type PG.