Action of pectic enzymes on oligogalacturonic acids and some of their derivatives

Abstract

Purified citrus pectinesterase (PE) does not hydrolyze the ester groups of ( a) the diester of digalacturonic acid, ( b) the diester of methyldigalacturonic acid, ( c) the triester of methyltrigalacturonic acid, or ( d) the half esters of digalacturonic acid. It readily attacks polygalacturonic acid polymethyl esters with D.P.'s of 10 and above. Purified fungal polygalacturonase (PG) does not hydrolyze the glycosidic galacturonide bonds of the three completely esterified oligogalacturonic acids, dimethyl ester of methyldigalacturonic acid, dimethyl ester of digalacturonic acid, or trimethyl ester of methyltrigalacturonic acid. It does not attack the glycosidic linkage of the half esters of digalacturonic acid. It hydrolyzes digalacturonic acid, methyl-α- d-digalacturonic acid, and trigalacturonic acid, but only at about 5% of the rate at which it attacks polygalacturonic acid. It attacks α- d-galacturonopyranosyl- l-galactonic acid. Thus PG attacks all polygalacturonide substrates which possess a glycosidic uronide bond between two adjacent free carboxyl groups, but fails to attack those where one or both of the adjacent carboxyl groups is esterified.