[Purification and properties of beta-D-mannanase from Nocardioform actinomycetes]

After cultivating in liquid medium for 3 days, an extracellular endo-1,4-beta-D-mannanase (EC-3.2.1.78) from a Nocardioform actinomycetes strain NA3-540 was purified 137-fold to electrophoretic homogeneity by ammonium sulfate precipitation, 95% alcohol precipitation, CM-sephadex A-50, hydroxyaptite column chromatography, DEAE-cellulose anion-exchange column chromatography and Sephadex G-100 column chromatography. The enzyme had a molecular mass of 41 kDa(by SDS-PAGE) and 40 kD (by gel filtration), a pI of 4.8 (PAGEIEF) and carbohydrates content of 3.5%. The enzyme was optimally active at pH 8 and 75 degrees C and showed stability at pH range of 6.5 to 12 at the temperature below 60 degrees C. The amino acid composition analysis of the enzyme proved that there were large amount of Gly, Asp, Ala and Glu. The enzyme was strongly inhibited by Hg2+, Cu2+, Pb2+, Fe3+, Co2+, Zn2+ and partly inhibited by Mn2+, Fe2+, Ag+ and slightly inhibited by Na+, K+, Li+, Mg2+, Ca2+, Ba2+.