Purification and Characterization of α-Mannosidase from Moss Hyophilla nymaniana (Fleish.) Menzel

Abstract

α-Mannosidase EC: (3.2.1.24) is the major post-translational modifications enzyme which catalyzes the cleavage of the alpha form of mannose. Lysosomal α-mannosidase assists in the processing of complex sugars from glycoproteins. Defective or deficient α-mannosidase activity causes α-mannosidosis and leads to deterioration of the central nervous system in children. In the present study, plant α-mannosidase was purified 39-fold in a stepwise manner by ammonium sulfate precipitation, dialysis, gel filtration chromatography and DEAE ion exchange chromatography. The purified mannosidase was a heterodimer consisting of approximately 72 and 50 kDa molecular mass subunits under reducing conditions. Optimum pH and temperature reported for mannosidase activity were 4.5 and 40 °C respectively. Among the various metal ions tested for the assessment of the enzyme activity, 2 mM Zn2+ strongly activated the enzyme while Hg2+and Ag2+ caused enzyme inhibition at the same concentration. The Km and Vmax values calculated from Lineweaver plot against the substrate p-nitrophenyl α-mannopyranoside were 5.4 mM and 8.4 U/ml, respectively. To the author’s knowledge, the data presented here is the first report on purification and characterization of α-mannosidase from the moss H. nymaniana.