Intracellular and extracellular free N-glycans produced by plant cells: occurrence of unusual plant complex-type free N-glycans in extracellular spaces.
As a part of the study to reveal the biological significance of de-N-glycosylation in plants, we analysed the structural features of free N-glycans (FNGs) accumulated inside cells and secreted to the extracellular space using a rice cell culture system. The structural analysis of FNGs obtained from the intracellular fraction revealed that the high-mannose type N-glycans with one GlcNAc residue (GN1-type) occurred at a concentration of ∼10 nmol/g, while the truncated complex type N-glycans with a N, N'-diacetylchitobiosyl unit (GN2-type) occurred at a concentration of ∼1 nmol/g. This result suggested that two kinds of glycoenzymes, cytosolic endo-β-N-acetylglucosaminidase (ENGase) and intracellular acidic peptide:N-glycanse (PNGase), are involved in the production of FNGs in rice cell as well as in other plant cells. On the other hand, in the culture medium, Lewis a epitope-containing complex and high-mannose type FNGs with the N, N'-diacetylchitobiosyl unit were found, suggesting extracellular acidic PNGase to be involved in the release of N-glycans from folded/processed glycoproteins in extracellular space. Furthermore, in the culture medium, we found unusual GN1-FNGs that have a biantennary complex type structure harbouring the Lewis a epitope, suggesting cytosolic ENGase and golgi N-glycan-processing enzymes to be involved in the production of these plant complex type FNGs.
Maeda
Megumi
M
Department of Biofunctional Chemistry, Graduate School of Natural Science and Technology, Okayama University, Tsushima-Naka 1-1-1, Okayama, Japan.
Kimura
Mariko
M
Kimura
Yoshinobu
Y
D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002460:Cell Line; D002846:Chromatography, Affinity; D002851:Chromatography, High Pressure Liquid; D005110:Extracellular Space / Q000502:physiology; D006023:Glycoproteins / Q000737:chemistry* / Q000502:physiology; D006026:Glycoside Hydrolases / Q000378:metabolism*; D042541:Intracellular Space / Q000502:physiology; D008969:Molecular Sequence Data; D012275:Oryza / Q000737:chemistry / Q000502:physiology; D011134:Polysaccharides / Q000737:chemistry / Q000502:physiology; D021241:Spectrometry, Mass, Electrospray Ionization
D006023:Glycoproteins; D011134:Polysaccharides; D006026:Glycoside Hydrolases