Bovine follicle-stimulating hormone (bFSH), a pituitary gonadotropin, is a heterodimer hormone that consists of a common alpha-subunit non-covalently associated with the hormone-specific beta-subunit. Unfortunately, expression levels of recombinant bFSH or its subunits are invariably low. We report here the secretory expression of biologically active bFSH alpha and bFSH beta subunit in the methylotrophic yeast Hansenula polymorpha. A slightly higher level of expression of recombinant bFSH subunits was achieved by using the Sacchromyces cerevisiae-derived calnexin (ScCne1) as a chaperone in engineered H. polymorpha strains. The preliminary data also suggested that bFSH subunits expressed in H. polymorpha appeared to be less-glycosylated. This isoform had been shown to be 80% increase in in vivo bioactivity compared with the hyperglycosylated Pichia pastoris-derived recombinant bFSH alpha/beta. More sophisticated applications of bFSH would profit from the assembled less-glycosylated heterodimer. (C) 2009 Elsevier Inc. All rights reserved.