Purification and characterization of polygalacturonase from banana fruit

Abstract

Polygalacturonase isoenzyme 3 (PG-3) was purified to homogeneity with a specific activity of 0.7 μ katal mg −1 protein from banana fruit pulp. The purified enzyme was a glycoprotein with ca. 8% carbohydrate. The molecular weight of the native enzyme was found to be 90 ± 10 kDa with a subunit molecular weight of 29 ± 2 kDa. The enzyme exhibited optimum activity at pH 4.3 and temperature 40°C with activation energy 35.4 kJ mol −1. A unique property of the enzyme was the requirement of –SH groups for the enzyme activity. The enzyme was inhibited by p-CMB and activated by 2-ME and DTT. The inhibition of p-CMB could be reversed by DTT. The enzyme contained eight free –SH groups. The K m of the enzyme was 0.15% for polygalacturonic acid.