Formation of deglycosylated α-L-fucosidase by endo-β-N-acetylglucosaminidase in Fusarium oxysporum

Abstract

Two forms of α-L-fucosidase, deglycosylated and glycosylated, were found in the fucose-inducing culture broth of Fusarium oxysporum. Endo-β-N-acetylglucosaminidase was also found in the same culture broth. The deglycosylated α-L-fucosidase was purified from the culture broth to homogeneity on polyacrylamide disc gel electrophoresis and analytical ultracentrifugation. Purified deglycosylated α-L-fucosidase was compared in chemical composition and immunological homology with glycosylated α-L-fucosidase which had been reported previously (K. Yamamoto, Y. Tsuji, H. Kumagai, and T. Tochikura, Agric. Biol. Chem. 50:1689, 1986). Both enzymes had nearly the same amino acid compositions and were immunologically identical. Glycosylated α-L-fucosidase had mannose, galactose, and N-acetylglucosamine residues. In contrast, the deglycosylated enzyme had only N-acetylglucosamine residues. These results suggest that the deglycosylated α-L-fucosidase is formed by the release of sugar chains from the glycosylated form by Fusarium endo-β-N-acetylglucosaminidase. Furthermore, various enzymatic properties were compared: the two α-L-fucosidases were found to exhibit similar catalytic activities and thermal stability profiles. The deglycosylated enzyme, however, was slightly unstable in the acidic pH range compared with the glycosylated enzyme.