EVIDENCE FOR SEVERAL GALACTAN SYNTHASES IN FLAX (LINUM-USITASSIMUM L)SUSPENSION-CULTURED CELLS

A membrane fraction from flax cells was able to incorporate [C-14]gala ctose from UDP-D-[C-14]galactose in vitro. The products of the reactio n, characterized by methylation analysis, consisted of a beta-1,4-gala ctan (solubilized mainly in water) and a beta-1,3-, beta-1,6-galactan (solubilized mainly in alkali). These results indicated the presence o f several galactan synthase complexes, as did a profile of the relatio nship between pH and activity which revealed both a maximum at pH 6.5 and a shoulder at pH 8. Moreover, galactan synthase activities were fo und 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 MgCl2) was achieved. The K(m) for UDP-galactose and V(max) were 38 muM and 4.5 nmol h-1 (mg protein)-1, respectively.