Abstract
Pectin lyase from the culture medium of Aspergillus japonicus was purified 122-fold by ammonium sulfate fractionation, Sephadex G-75 gel filtration, DEAF-Sephadex treatment, SE-Sephadex column chromatography, and Sephadex G-100 gel filtration. The purified enzyme was free from pectinesterase and endo-polygalacturonase, and was homogeneous on ultracentrifugal analysis. The isoelectric point and the sedimentation coefficient of the enzyme were at pH 7.7 and 3.4 S, respectively. Molecular weight of the enzyme by using gel filtration was estimated to be 32, 000. The pH optimum of the enzyme for pectin was 6.0, but was 7.0 for polymethyl polygalacturonate methyl glycoside. The addition of calcium ion stimulated the activity and shifted the pH optimum to 7.0, only when pectin was used as substrate. A marked inhibition of the activity was observed by oxidizing reagents such as iodine and N-bromosuccinimide, although hydrogen peroxide did not inhibit the activity. Metal chelating reagents, reducing reagents and sulfhydryl inhibitors did not affect the activity. The purified enzyme was able to macerate parenchymateous tissues, in which onion tissue was the most susceptible one to be attacked by the enzyme.
