Evidence for Several Galactan Synthases in Flax (Linum usitassimum L.) Suspension-Cultured Cells

概要

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A membrane fraction from flax cells was able to incorporate [^<14>C]galactose from UDP-D-[^<14>C]galactose in vitro. The products of the reaction, characterized by methylation analysis, consisted of a β-1 ,4-galactan (solubilized mainly in water) and a β-1,3-, β-1,6-galactan (solubilized mainly in alkali). These results indicated the presence of several galactan synthase complexes, as did a profile of the relationship between pH and activity which revealed both a maximum at pH 6.5 and a shoulder at pH 8. Moreover, galactan synthase activities were found at two densities: 1.125 g cm^<-3> (Golgi membranes) and 1.07-1.08 g cm^<-3> (corresponding to low-density vesicles). Partial characterization of one enzymatic system (maximaly active at pH 8 in the presence of 5 mM MgCl_2) was achieved. The K_m for UDP-galactose and V_<max> were 38μM and 4.5 nmol h^<-1> (mg protein)^<-1>, respectively.
日本植物生理学会の論文