Biochemical properties of extracellular alpha -mannosidases from the digestive fluid of Rhynchophorus palmarum larvae

Three extracellular [alpha]-mannosidases (EC 3.2.1.24) were purified from the digestive fluid of oil palm weevil larvae. Rhynchophorus palmarum (L.) and characterized in order to explore their potential for biotechnological application. Three steps procedure including size exclusion, anion exchange and hydrophobic interaction chromatography were Used. The enzymes named Rp/M1, Rp/M2 and Rp/M3 had native molecular weights of approximately 125, 72 and 111 kDa, respectively and functioned as dimeric (Rp/M1) and monomeric (Rp/M2 and Rp/M3) Structures. The three [alpha]-mannosidases displayed acidic and mesophilic activities by using para-nitrophenyl-[alpha]-D-Mannopyranoside as substrate. Apparent KM values were found to be 0.13, 0.22 and 0.16 nM for Rp/M1, Rp/M2 and Rp/M3, respectively. Ba2+, Ca2+, Mg2+, Zn2+ and ethylene diamine tetra acetic acid (EDTA) had no effect oil the three enzyme activities whereas detergents and reducing agents were inhibitors. Rp/M1, Rp/M2 and Rp/M3 were more sensitive to swainsonine and cleaved [alpha]-1,2: [alpha]-1,3 and [alpha]-1.6 linked mannobioses. These characteristics prompted LIS to categorize them as catabolic [alpha]-mannosidases. Thus, they would help in the larval oil palm weevil nutrition allowing digestion by the removal of mannose residues in the beetle's diet. Also, these enzymes could find potential application in biological, biochemical and pharmaceutical area.