Abstract
The structure of the xyloglucan synthesised in vitro by the particulate fraction of suspensioncultured soybean (Glycine max) cells from UDP-glucose and UDP-xylose is mainly composed of two kinds of oligosaccharide-building blocks, a heptasaccharide unit and a pentassaccharide unit [T. Hayashi and K. Matsuda, J. Biol. Chem., 256, 11117 (1981)]. The synthesis of the pentasaccharide unit is probably the first step in the construction of oligosaccharide building blocks to elongate the β-1, 4-glucan backbone. This enzymatically synthesized xyloglucan was shown to have the same molecular size (Mw, 180, 000) as the xyloglucan prepared from soybean cell walls by gel filtration on a Sepharose CL-6B column, and the same building blocks distributed among each fraction. A pulse-chase experiment indicated that the pentasaccharide unit was converted into the heptasaccharide unit. The conversion was regulated by the concentration of UDP-xylose.
