Purification and Characterization of Intracellular α-Glucuronidase from Aspergillus niger 5-16

Abstract

Two kinds of α-glucuronidases, CM-I and CM-II, were purified from a cell-free extract of Aspergillus niger 5-16. Molecular weights of both CM-I and CM-II were 130, 000 by SDS-PAGE, and 150, 000 by gel filtration. The optimum temperature and pH for the both enzyme reactions were 60°C and 4.8. Both enzymes were stable up to 50°C, and between pHs 4.5 to 7.0 for 1 hr. Both enzymes were strongly inhibited by Ag⁺, Hg²⁺, Pb²⁺, Sn²⁺, Fe²⁺, Fe³⁺, Al³⁺, sodium dodecyl sulfate, monoiodoacetic acid, and N-bromosuccinimide. The K_m of CM-I toward glucuronosyl-xylotriose and 4-O-methyl-glucuronosyl-xylotriose were 0.77 and 0.37, and those of CM-II were 0.82 and 0.47 mM, respectively. The V_max of CM-I toward glucuronosyl-xylotriose and 4-O-methyl-glucuronosyl-xylotriose were 5.20 and 1.42, and those of CM-II were 17.1 and 4.68 μmol of glucuronic acid formed/min/mg of protein, respectively.