Regulated secretory proteins are sorted via selective co-aggregation in eukaryotes, Cellobiase (C) of the filamentous fungus Termitomyces clypeatus remained co-aggregated with sucrase (S). and only one isoform of each of the enzymes was present in intra- and extracellular extracts. Kinetics of secretion of sucrase increased in vivo and in vitro in secreting (Sc) medium and decreased under non-secreting (NSc) conditions similar to those observed for cellobiase. In the Sc condition, total enzyme production and activity ratios of cellobiase and sucrase (C/S) in cell-bound, extra- and intracellular preparations increased with time and were significantly higher from those obtained in non-secretory media. It was concluded that secretion of sucrase in culture medium is under same cellular regulation as that of cellobiase, and sucrase is involved in regulating extracellular release of cellobiase through co-aggregation in the fungus.