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Properties of a Polygalacturonase Produced by Geotrichum candidum. I. Barash, Division of Mycology and Plant Pathology, Department of Botany, Tel Aviv University, Tel Aviv, Israel; Z. Eyal, Division of Mycology and Plant Pathology, Department of Botany, Tel Aviv University, Tel Aviv, Israel. Phytopathology 60:27-30. Accepted for publication 27 June 1969. DOI: 10.1094/Phyto-60-27.

A polygalacturonase was purified approximately 19-fold from culture filtrates by carboxymethyl cellulose column chromatography. Results obtained by ion exchange chromatography, disc electrophoresis, and temperature inactivation of the polygalacturonase suggested the presence of a single enzyme. The enzyme cleaved pectic acid by a random mechanism of hydrolysis. Liberation of monogalacturonic acid was observed immediately at the onset of the reaction. The reaction proceeded linearly until it attained 40% hydrolysis of which galacturonic acid release accounted for 5% of the total galacturonic bonds split. After a 2-hr reaction period, the total hydrolysis of pectic acid was 55%, 15% of which was accounted for by galacturonic acid accumulation. The pH optimum, as measured by viscosity decrease, coincided with that required for monogalacturonic acid formation. The pH optimum for trigalacturonic acid as a substrate was 3.5 as compared to pH 4.5-5 for sodium polypectate. Trigalacturonic acid was slowly split to di- and monogalacturonic acid, but digalacturonic acid was not attacked. The enzyme was, therefore, classified as endopolygalacturonase.