The methylotrophic yeast, Pichia pastoris, has been used to co-express recombinant genes formed by fusion of the mating factor-alpha (MF ) leader and ovine follicle stimulating hormone (oFSH) and subunit coding sequences. Pichia strains carrying single copies of the two fusion genes secreted recombinant oFSH (roFSH) to concentrations of approximately 51·0 ng/ml and 17·5 ng/ml, measured by RIA or in vitro bioassay respectively, whereas a strain with two copies of the and one copy of the subunit

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... usion genes secreted roFSH to concentrations of 61 ng/ml (RIA) and 22 ng/ml (bioassay). It appears that the Pichia-derived roFSH had about one-third the in vitro bioactivity of native oFSH or, alternatively, only one-third of the roFSH is bioactive. Measurements of secreted roFSH and subunit concentrations indicated less than 10% of and 25-33% of subunits were stably dimerized. The receptor binding properties of the roFSH resemble those of native oFSH. In summary this paper reports the production, by P. pastoris, of a heterodimeric glycoprotein hormone (roFSH) that has in vitro biological activity.