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-beta-N-acetylglucosaminidases (endo-beta-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 alpha 1-2 mannosyl residue(s), Man(9-6)GlcNAc(2)-PA (PA is pyridylamino) (80-100% relative hydrolysis), were most favored substrates followed by Man(5)GlcNAc(2)-PA (32% for Endo-LE, 43% for Endo-GM), a typical hybrid-type structure (GlcNAc(1)Man(5)GlcNAc(2)-PA; 34% for Endo-LE, 37% for Endo-GM), and then the common core pentasaccharide of N-glycan (Man(3)GlcNAc(2)-PA; 9% for Endo-GM and 16% for Endo-LE). On the contrary, both Endo-GM and Endo-LE could bar:ly hydrolyze the xylose-containing N-glycans (Man(3)Xyl(1)GlcNAc(2)-PA, Man(3)Fuc(1)Xyl(1)GlcNAc(2)-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 Man(6)GlcNAc(2)-PA in a weak acidic region (pH 6.0-6.5). (C) 1998 Elsevier Science B.V. All rights reserved.