Purification and Characterization of Alkaline Xylanase Secreted from Paenibacillus macquariensis

An alkaline xylanase secreted by Paenibacillus macquariensis RC 1819 has been purified using ammonium sulfate fractionation, ion exchange chromatography using DEAE-cellulose and gel filtration chromatography over Sephadex G-200 and Sephadex G-100. The purified enzyme had the specific activity, 25.2 units/mg protein with birchwood xylan as a substrate. The purified enzyme showed a single protein band over sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The molecular weight of the enzyme has been found to be 31,000 ± 2000 as determined by using Sephadex G-200 gel filtration chromatography. The subunit molecular weight has also been found to be ~31,000 as determined using SDS-PAGE indicating monomeric enzyme. The enzyme showed optimum activity at pH 8.6 and temperature, 50 ̊C. The Michaelis constant (Km) of the enzyme for birchwood xylan was 2.2 mg/ml as determined using velocity saturation plot. The metal ions viz. Co and Mn stimulated xylanase enzyme activity whereas Hg inhibited the enzyme activity.