Carboxylesterase 2 production and characterization in human cells: new insights into enzyme oligomerization and activity

Carboxylesterase 2 (CES2), the main carboxylesterase expressed in human intestine, is an increasingly important enzyme in anti-cancer combined therapies for the treatment of different pathologies like colon adenocarcinoma and malignant glioma. The production of human recombinant CES2, in human embryonic kidney cells (HEK-293T cells) using serum-free media, is herein described. CES2 secretion to the media was achieved by the simple addition of an in-frame C-terminal 10× histidine tag (CES2-10xHis) without the need of addition of extra N-terminal signalling sequences or the mutation or deletion of the C-terminal HTEL motif responsible for retaining the protein in the lumen of endoplasmic reticulum. This secretion allowed a fourfold increase in CES2 production. The characterization of human recombinant CES2 showed that this protein exists in other active and inactive forms than the described 60 kDa monomer.