Thermostable and alkalistable exopolygalacturonase of Bacillus pumilus dcsr1: Characteristics and applicability.

The bioactive form of thermostable and alkali stable pectinase of Bacillus pumilus dcsr1 is a homodimer of the molecular mass of 60 kDa with a pI of 4.6. The enzyme is optimally active at 50 °C and pH 10.5, and its Michaelis constant (Km), maximum rate of reaction (V), activation energy (E), and temperature quotient (Q) values (for citrus pectin) are 0.29 mg mL, 116 μmole mg min, 74.73 KJmol and 1.57, respectively. The enzyme has a shelf life of one and a half years at room temperature as well as 4 °C. The activity of the enzyme is stimulated by Mn and Ca and inhibited by Hg, Cd, Co, Zn, Fe, Pb, EDTA and urea to a varied extent. The conformational studies of the enzyme revealed a high β-sheet content in the bioactive dimer, and high α-helix in the inactive monomer. The Circular Dichroism (CD) spectra of the dimer in the presence of inhibitors suggested a marked decrease in β-sheet, and a significant increase in α-helix, suggesting a key role of β-sheets in the enzyme catalysis. Based on the end product analysis, the enzyme is an exopolygalacturonase with a unique ability of transglycosylation. When ramie fibers were treated with the enzyme, removal of gummy material (pectin) was visible, confirming its applicability in the degumming process.