PLANT PHYSIOLOGY , Vol 106, Issue 2 779-784, Copyright © 1994 by American Society of Plant Biologists
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METABOLISM AND ENZYMOLOGY |
Carbon Starvation Increases Endoglycosidase Activities and Production of "Unconjugated N-Glycans" in Silene alba Cell-Suspension Cultures
S. Lhernould, Y. Karamanos, B. Priem and H. Morvan
Laboratoire de Biologie Cellulaire Vegetale et Valorisation des Especes Ligneuses (S.L., H.M.), Institut de Biotechnologie, Universite de Limoges, 123, Avenue Albert Thomas, 87060 Limoges Cedex, France (Y.K.)
We previously reported the occurrence of oligomannosides and xylomannosides
corresponding to unconjugated N-glycans (UNGs) in the medium of a white
campion (Silene alba) cell suspension. Attention has been focused on these
oligosaccharides since it was shown that they confer biological activities
in plants. In an attempt to elucidate the origin of these oligosaccharides,
we studied two endoglycosidase activities, putative enzymes involved in
their formation. The previously described
peptide-N4-(N-acetyl-glucosaminyl) asparagine amidase activity and the
endo-N-acetyl-[beta]-D-glucosaminidase activity described in this paper
were both quantified in white campion cells during the culture cycle with
variable initial concentrations of sucrose. The lower the sucrose supply,
the higher the two activities. Furthermore, endoglycosidase activities were
greatly enhanced after the disappearance of sugar from the medium. The
production of UNGs in the culture medium rose correlatively. These data
strongly suggest that the production of UNGs in our white campion
cell-suspension system is due to the increase of these endoglycosidase
activities, which reach their highest levels of activity during conditions
of carbon starvation.
