Possible Role of Cell Wall Mannan in the Secretion of the Protopectin-solubilizing Enzyme of Trichosporon penicillatum SNO-3

Abstract

The extracellular production of a protopectin-solubilizing enzyme (protopectinase) of Trichosporon penicillatum SNO-3 decreased when peptone was used as the nitrogen source. Peptone caused a morphological change in the microorganism. Cells cultured in the presence of peptone were elongated (E-cells), but those cultured in the absence of peptone were yeast shaped (N-cells). E-cells contained less cell wall mannan than N-cells. When cells were converted into protoplasts, protopectinase was liberated from N-cells together with polysaccharides, but not from E-cells. The sugar moiety of the protopectinase was identified. The enzyme contained 2 residues of glucosamine and 0.7 residues of mannose per molecule. The presence of protopectinase on the cell surface was monitored by means of immunofluorescence and enzyme immunoassays, which showed that the enzyme protein was present on the surfaces of both N- and E-cells. The results obtained suggested that cell wall mannan affects the secretion of this enzyme, and that E-cells cannot secrete the enzyme because they are deficient in cell wall mannan.