PURIFICATION AND CHARACTERIZATION OF PECTIN LYASE-B, A NOVEL PECTINOLYTIC ENZYME FROM ASPERGILLUS-NIGER

An Aspergillus niger multicopy pki-pelB fusion transformant was used t o overexpress pectin lyase B. Under the control of this glycolytic pro moter no other contaminating extracellular pectinolytic enzymes appear ed in the culture fluid. PL B could thus be purified easily. It has a molecular mass of 40 kDa and has been characterized as an endo-acting enzyme. The iso-electric point of PL B (5.9) is much higher than the p I-values of two other A. niger pectin lyases viz. pI 3.65 for PL I and pI 3.75 for PL II). Other differences between this enzyme and the two other well characterized pectin lyases are the much higher pH optimum and the higher turnover number on highly esterified pectin for PL B.