Pectic Enzymes and Development of the Pear (Pyrus communis)

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Abstract
SUMMARY—: Changes in firmness, protein, pectinesterase (PE) and polygalacturonase (PG) were followed during enlargement, maturation, and abnormal ripening of the Bartlett pear ( Pyrus communis ) on the tree. Although the PE activity per pear increased during maturation, with a good correlation with total weight ( r = 0.93 and 0.87 for 1962 and 1963), the amount of activity per gram fresh weight and per milligram protein decreased. There was a high correlation between PE activity and protein ( r = 0.84 and 0.91 for 1962 and 1963). The specific activity of the enzyme decreased during maturation. As the fruit matured and ripened on the tree, the percent recovery of PE decreased. The use of polyvinylpyrrolidone in the extraction procedure to adsorb the phenolic compounds counteracted this trend. It was concluded that the small changes in PE activity could not account for the changes in esterification of pectin observed by other investigators. Variable results were obtained with the PG assays. Weak PG activity was observed in the immature fruit in 1962 and 1963. No activity was observed in 1966, even in the presence of polyvinylpyrrolidone.

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