[Pichia pastoris X-33 with OCH1 gene deletion and its expression of glycoprotein GM-CSF].

Objective: Glycoproteins derived from yeast expression systems are usually hyperglycosylated and contain non human N-glycans of the high mannose type. alpha-1, 6-mannosyltransferase (och1p) plays a key role in modifying glycoproteins with high mannose-type N-glycans. Therefore, we engineered a P. pastoris X-33 strain with OCH1 gene deletion. This strain was further used as a host for production of glycoproteins with smaller N-glycans.

Methods: First, we knockout the URA3 gene of P. pastoris X-33 which encoding orotidine-5'-phosphate decarboxylase by double homologous recombination. Then, we knockout OCH1 gene using URA3 gene as a selecting marker, and obtained X-33 (och1-) strain. After that, this mutant strain was used to expression the glycoprotein granulocyte-macrophage colony-stimulating factor (GM-CSF).

Results: Different from hyperglycosylated GM-CSF expressed in wild type P. pastori X-33, the glycoprotein expressed in X-33 (och1-), containing smaller N-glycan.

Conclusion: The results suggested that X-33 (och1-) strain can be used as an expression host for production of glycoproteins lacking the outer-chain hypermannoses, and a host could be used for further N-glycosylation engineering.