Role of (1,3)(1,4)-β-Glucan in Cell Walls: Interaction
with Cellulose
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Abstract
(1,3)(1,4)-β-d-Glucan (mixed-linkage glucan or MLG),
a characteristic hemicellulose in primary cell walls of grasses, was
investigated to determine both its role in cell walls and its interaction
with cellulose and other cell wall polysaccharides in vitro. Binding
isotherms showed that MLG adsorption onto microcrystalline cellulose
is slow, irreversible, and temperature-dependent. Measurements using
quartz crystal microbalance with dissipation monitoring showed that
MLG adsorbed irreversibly onto amorphous regenerated cellulose, forming
a thick hydrogel. Oligosaccharide profiling using <i>endo</i>-(1,3)(1,4)-β-glucanase indicated that there was no difference
in the frequency and distribution of (1,3) and (1,4) links in bound
and unbound MLG. The binding of MLG to cellulose was reduced if the
cellulose samples were first treated with certain cell wall polysaccharides,
such as xyloglucan and glucuronoarabinoxylan. The tethering function
of MLG in cell walls was tested by applying <i>endo</i>-(1,3)(1,4)-β-glucanase
to wall samples in a constant force extensometer. Cell wall extension
was not induced, which indicates that enzyme-accessible MLG does not
tether cellulose fibrils into a load-bearing network