Enzymatic properties of endo-β-N-acetylglucosaminidases from developing tomato fruits and soybean seeds: substrate specificity of plant origin endoglycosidase

Substrate specificity and some other enzymatic properties of partial purified endo-β-N-acetylglucosaminidases (endo-β-GlcNAc-ase) from developing soybean seeds (Glycine max, Endo-GM) and developing tomato fruits (Lycopersicum esculentum, Endo-LE) were studied. The substrate specificity of these two endoglycosidases was explored and compared with regard to various pyridylaminated N-glycans derived from some naturally occurring glycoproteins. For Endo-GM and Endo-LE, several high mannose-type sugar chains bearing α1-2 mannosyl residue(s), Man_9-6GlcNAc₂-PA (PA is pyridylamino) (80-100% relative hydrolysis), were most favored substrates followed by Man₅GlcNAc₂-PA (32% for Endo-LE, 43% for Endo-GM), a typical hybrid-type structure (GlcNAc₁Man₅GlcNAc₂-PA; 34% for Endo-LE, 37% for Endo-GM), and then the common core pentasaccharide of N-glycan (Man₃GlcNAc₂-PA; 9% for Endo-GM and 16% for Endo-LE). On the contrary, both Endo-GM and Endo-LE could barely hydrolyze the xylose-containing N-glycans (Man₃Xyl₁GlcNAc₂-PA, Man₃Fuc₁Xyl₁GlcNAc₂-PA) found ubiquitously in plant cells. The molecular mass of these two endoglycosidases was approximately 62 kDa by gel filtration and both Endo-GM and Endo-LE showed maximal activities for Man₆GlcNAc₂-PA in a weak acidic region (pH 6.0-6.5). Copyright (C) 1998 Elsevier Science B.V.