ISOLATION AND PARTIAL-PURIFICATION OF MANNOSE-SPECIFIC AGGLUTININ FROM BREWERS-YEAST INVOLVED IN FLOCCULATION

Yeast cell-agglutinating activity, designated agglutinin (possible lec tin), was isolated from cell walls of both non-flocculent and floccule nt brewer's yeast cells. Agglutinin-mediated aggregation of yeast cell s in a manner similar to flocculation with respect to specific mannose -sensitivity, pH-dependence and calcium-dependence. Agglutinating acti vity was found to be heat-stable and protease-insensitive. Furthermore , addition of agglutinin to flocculent cells strongly stimulated the f locculation ability of the cells, whereas addition to non-flocculent c ells rendered these cells weakly flocculent. Agglutinin was found to b e released from flocculent cells during the course of a flocculation a ssay, but not from non-flocculent cells. Presence of mannose during th e assay inhibited release of agglutinin. Our results suggest that (i) mannose-specific agglutinin is continuously synthesized during growth of brewer's yeast cells, (ii) agglutinin is present in cell walls of n on-flocculent cells but is unable to bind its ligand on other cells, a nd (iii) the ability of yeast cells to flocculate in a flocculation as say depends, among other factors, on release of agglutinin from the ce lls. A 10-kDa polypeptide might represent one form of agglutinin.