PURIFICATION OF AN ELICITOR-INDUCED GLUCAN SYNTHASE (CALLOSE SYNTHASE) FROM SUSPENSION-CULTURES OF FRENCH BEAN (PHASEOLUS-VULGARIS L.) - PURIFICATION AND IMMUNOLOCATION OF A PROBABLE M-R-65-000 SUBUNIT OF THE ENZYME

Membrane preparations from suspension-cultured cells of French bean (P haseolus vulgaris is P.) contained callose synthase (EC 2.4.1.34) acti vity which was preserved upon solubilisation. Following elicitor treat ment of cell cultures, increased activity could be extracted and this increase was maintained during purification. The enzyme was purified b y high-pressure liquid chromatography and active fractions showed a va riable association of two polypeptides of relative molecular masses (M -r.) 55 000 and 65 000, the latter being in excess. The M-r-65 000 pol ypeptide was purified to homogeneity and an antibody raised to it. Thi s antibody showed complex effects on callose synthase activity when in cubated with membrane and soluble extracts. In comparison with other s ystems, the M, 55 000 subunit is likely to represent the catalytic sub unit while the M-r-65 000 polypeptide is a possible regulatory subunit . The M-r-65 000 polypeptide was immunolocated in membranes at sites o f callose synthesis in the plant, in cell plates. in sieve plates. at the plasma membrane-wall interface of wounded cells and in papillae in infected cells.