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Abstract

Exo-D-galacturonanase (E.C.3.21.67) was obtained from the aqueous extracts of banana peel by salting out with ammonium sulfate and separating the mixture of proteins on a DEAE Sephadex A-50 packed column followed by a gel filtration through Sephadex G-100 and Sephadex G-75. The purified enzyme was stable in acid medium up to 50 °C. The pH optimum for the action of exo-D-galacturonanase depended upon the chain length of the degraded substrate and was found to be 4.4 for di- and tetragalacturonic acids, 4.6 for hexa- and heptagalacturonic acids, and 4.9 for polygalacturonic acid. The chain length of galacturonan affected action of the enzyme. Oligomer of polymerization degree D_p = 6 was the optimal substrate. The enzyme was classified as an exo-D-galacturonanase on the basis of its terminal mode of action, the ability to cleave digalacturonic acid and the decrease of viscosity in relation to the number of cleaved glycosidic bonds.