To provide strains of the genus Pichia which are deficient in proteolytic activity, and to provide a means for generating such strains.

The isolation and characterization of genes involved in proteolytic processing in species of the genus Pichia and the availability of such genes enable the generation of the strains of Pichia which are deficient in proteolytic activity and useful as hosts for the expression of proteolytically sensitive recombinant products. The isolation and characterization of additional genes from species of the genus Pichia are also provided, as well as uses thereof.