pGAPZ A, B, & C and pGAPZ A, B, & C are expression vectors designed for high-level, constitutive expression in Pichia pastoris. pGAPZ and pGAPZ were created by replacing the methanol-regulated AOX1 promoter with the constitutive, glyceraldehyde-3-phosphate dehydrogenase (GAP) promoter in the backbone of the pPICZ vectors. Although the yield of any protein constitutively expressed in the Pichia system is dependent on the toxicity of the protein to yeast, constitutive expression under the control of pGAPZ or pGAPZ vectors can sometimes produce greater yields than inducible expression (1).