Co-operative action by endo- and exo-beta-(1 leads to 3)-glucanases from parasitic fungi in the degradation of cell-wall glucans of Sclerotinia sclerotiorum (Lib.) de Bary.

1. Two fungi, Coniothyrium minitans Campbell and Trichoderma viride Pers. ex Fr., were grown on autoclaved crushed sclerotia of the species Sclerotinia sclerotiorum, which they parasitize. 2. In vitro the crude culture filtrates would lyse walls isolated from hyphal cells or the inner pseudoparenchymatous cells of the sclerotia, in which a branched beta-(1-->3)-beta-(1-->6)-glucan, sclerotan, is a major constituent. 3. Chromatographic fractionation of the enzymes in each culture filtrate revealed the presence of several laminarinases, the most active being an exo-beta-(1-->3)-glucanase, known from previous studies to attack sclerotan. Acting alone this brought about a limited degradation of the glucan, but the addition of fractions containing an endo-beta-(1-->3)-glucanase led to almost complete breakdown. A similar synergism between the two enzymes was found in their lytic action on cell walls. 4. When acting alone the endo-beta-(1-->3)-glucanase had a restricted action, the products including a trisaccharide, tentatively identified as 6(2)-beta-glucosyl-laminaribiose. 5. These results are discussed in relation to the structure of the cell walls and of their glucan constituents.