Expression of human cathepsin E in methylotrophic yeast, Pichia pastoris

The human gastric cathepsin E (CTSE) was expressed in the methylotrophic yeast Pichia pastoris by placing the CTSE cDNA under the control of the methanol-inducible alcohol oxidase promoter. The human CTSE expressed in P. pastoris was efficiently secreted into the culture medium as an active enzyme directed by its native signal sequence, whereas CTSE has been shown to be retained in mammalian tissue cells. The recombinant human CTSE was secreted as a 90-kDa molecule and then converted via an 84-kDa intermediate to an 82-kDa molecule. The 90-kDa molecule and the 82-kDa molecule were considered to be the proenzyme and the mature enzyme as dimeric forms, respectively.