The signal peptide of Aspergillus oryzae endo-(1,4)-beta-xylanase XynF1 contains a C-terminal serine-arginine that directs efficient secretion of the enzyme into the culture medium. In the basidiomycete Coprinus cinereus, however, there is little secretion of XynF1 into the culture medium. Modification of the C-terminal sequence of the signal peptide to lysine-arginine resulted in efficient secretion of C. cinereus XynF1, suggesting the presence of a KEX2-like protease in this fungus.