Hydrolysis of the oligogalacturonides and pectic acid by yeast polygalacturonase.

Yeast polygalacturonase (YPG) is a constitutive type enzyme, produced exocellularly and free of pectinesterase by Saccharomyces jragilis (1). It has an optimal pH of 4.4 and appears to be specific in its activity towards polygalacturonides (2). YPG differs from preparations of commercial fungus polygalacturonase in that it cannot carry out a complete breakdown of pectic acid to galacturonic acid. If the hydrolysis is carried out at pH 5.0, the compounds present when the reaction slows down to an extremely low rate (about 48 per cent glycosidic hydrolysis) are a mixture of tri-, di-, and monogalacturonic acids (3, 4). The same three products are formed by enzyme preparations from Aspergillus foetidus (grown in a submerged culture) at pH 5.5 (5) and by tomato extracts at pH 4.5 (6) on pectic acid. In the present paper, we have studied the action of YPG on pectic acid and on di-, tri-, tetra-, and pentagalacturonic acids at different pH values. This comparative study has enabled us to explain more fully the behavior of YPG on the parent compound, pectic acid.