Enzymatic Properties of a Ginkgo biloba Endo-β-N-acetylglucosaminidase and N-Glycan Structures of Storage Glycoproteins in the Seeds

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An endo-β-N-acetylglucosaminidase has been purified to homogeneity from mature seeds of Ginkgo biloba. The molecular mass of the endo-β-N-acetylglucosaminidase, named Endo-GB, was estimated to be around 63 kDa by SDS-PAGE and around 62 kDa by Hiprep S-200 chromatography, respectively. The substrate specificity has been explored with regard to the pyridylaminated N-glycans. Several high mannose-type sugar chains bearing α-1, 2-mannosyl residue(s), Man_9-6GlcNAc_2-PA, were the most favored substrates followed by Man_5GlcNAc_2-PA and a typical hybrid-type structure (GlcNAc_1Man_5GlcNAc_2-PA) which does not bear an α-1, 2-mannosyl residue. On the contrary, endo-GB could hardly hydrolyze the common core pentasaccharide of N-glycan (Man_3GlcNAc_2-PA) and the xylose-containing sugar chains (Man_4-3Xyl_1GlcNAc_2-PA, Man_3Fuc_1Xyl_1GlcNAc_2-PA) being widely distributed in plant glycoproteins. Furthermore, we analyzed the structures of N-glycans conjugated to storage glycoproteins in the mature Ginkgo seeds to see the occurrence of endogenous substrates for Endo-GB. The structural analysis showed, however, only xylose-containing type N-glycans (Man_3Fuc_1Xyl_1GlcNAc_2 (95%) and Man_3Xyl_1GlcNAc_2 (5%)), which can not be substrate for Endo-GB, predominantly occur in the storage glycoproteins.
社団法人日本農芸化学会の論文
1998-02-23