What are the limitations of the yeast protein expression system?

One drawback is the limited choice of vectors. Another limitation is the presence of active proteases that degrade foreign proteins, and as a result reduce their yield. There is also the lack of a strong and highly regulated promoter when using these systems. Another disadvantage is the secretion efficiency is low. Target protein molecules with a molecular mass greater than 30 KD are hardly secreted. The glycosylation pattern differs from that of humans and other mammalian cells. Lastly, this system experiences the unresolved biological activity of certain expressed proteins due to incorrect folding and lack of necessary cofactors.