The Role of Calcium Ions in Restoring Lipase Activity of Recombinant Human Lipoprotein Lipase Expressed in Bacteria

Lipoprotein lipase (LPL) is a blood vessel lipase that regulates and removes plasma lipoprotein triglycerides from blood circulation. It is important in the control of hypertriglyceridemia. LPL dysregulation can lead to hypertriglyceridemia and increase the risk of atherosclerosis cardiovascular disease. Therefore, the biochemical characterization of LPL could help understand the LPL dysregulation mechanism. However, active LPL enzyme acquisition via bacterial expression is challenging, as studies have reported that LPL could only be co-expressed in the presence of a chaperone. Therefore, this work intends to investigate the possibility of bacterial expression of human LPL (hLPL) with active lipase activity. The hLPL protein has been produced in SHuffle® T7 cells, and the optimal refolding conditions of the hLPL protein have been described here. The addition of 4% glycerol, 0.5-M NaCl, and 0.5-mM CaCl₂ in the refolding buffer has improved the hLPL lipase activity in the p-nitrophenol butyrate assay. The hLPL protein showed improved lipase activity with V_max and K_m of 14.84 nmol/min/mg and 0.77 mM at 37 °C, respectively. These results indicate that the bacteria expression system could be an alternative approach to produce recombinant hLPL.