Purification and properties of a galacturonic acid-releasing exopolygalacturonase from a strain of Bacillus

In esopolygalacturonase [exo-PC;ase; poly (1,4-alpha -D-galacturonide) gala cturonohydrolase, EC; 3.2.1.67] was found to be extracellularly produced by Bacillus sp. strain KSM-P443. The exo-PGase was purified to homogeneity, a s judged by polacrylamide gel electrophoresis, through sequential column ch romatographies. If he enzyme had a molecular weight of approximately 45.000 and an isoelectric point of pH 5.8. The N-terminal sequence was Ser-Met-Gl n-Lys-Ile-Lys-Asp-elu-Ile-Len-Lys. Thr-Leo-Eys-Val Phe and had no sequence similarity to those of ether pectinolytic enzymes reported to date. Maximum activity toward polypalacturonic acid (PGA) was observed at 60 degreesC an d at pH 7.0 in 100 mM Tris-HCl buffer without requiring any metal ions. Whe n the chain length of aligogalacturonic acids increased, the apparent Km fo r them decreased, but the h-cat values increased. This is tile first bacter ial eso-Pease that releases exclusively mono-galacturonic acid from PGA, di -, tri-, tetra-, and penta-galacturonic acids.