BIOCHEMICAL CHARACTERIZATION OF A NOVEL β‐ N ‐ACETYLHEXOSAMINIDASE FROM THE INSECT OSTRINIA FURNACALIS

The β‐ N ‐acetylhexosaminidase FDL specifically removes the β‐1,2‐ G lc NA c residue conjugated to the α‐1,3‐mannose residue of the core structure of insect N ‐glycans, playing significant physiological roles in post‐translational modification in the G olgi apparatus. Little is known about its enzymatic properties. We obtained the O f FDL gene from the insect O strinia furnacalis by RT ‐ PCR . The full length c DNA of FDL is 2241 bp carrying an opening reading frame of 1923 bp encoding 640 amino acids. The recombinant protein O f FDL in a soluble and active form was obtained with high purity through a two‐step purification strategy. The recombinant O f FDL exclusively hydrolyzes the terminal β‐1,2‐ G lc NA c residue from the α‐1,3 branch instead of the α‐1,6 branch of the substrate G n G n‐ PA . Several kinetic parameters including k cat /K m values toward four artificial substrates and K i values of three representative hexosaminidase inhibitors were obtained.