Abstract
Rhamnogalacturonan I, a component of pectic polysaccharides, consists of a backbone of repeating disaccharide unit, →αGalA1→2αL-Rha→, attached with sugar-chains of (1→4)-linked β-Galp and/or (1→5)-linked α-L-Araf residues at C-4 of L-Rha residues. The side-chains regulate intercellular attachment, thereby affect the architecture of cell walls. We have analyzed the enzymatic properties of a membrane-bound galactosyltransferase (GalT) prepared from etiolated soybean hypocotyls (Planta, in press). We have attempted to solubilize and purify the GalT protein to identify the corresponding gene.
Activity of GalT was assayed by measurement of the amount Gal groups transferred from UDP-[14C]Gal onto β-(1→4)-galactan as an acceptor. By the treatment of the microsomal fraction with 0.75% Triton X-100, more than 70% of GalT activity could be solubilized. Subsequent chromatography of the solubilized fraction on a CM-Sepharose column followed by affinity chromatography separated a large amount of impurity from the enzyme protein.
