Functional analysis of a mimetic peptide of human hepatic lipase

Human hepatic lipase (HL) is an enzyme that is electrostatically bound to the cell surface via heparan sulfate proteoglycans (HSPG). HL functions as a homodimer to hydrolyze triglycerides and phospholipids within circulating lipoproteins. Its activity can be detected in circulation after heparin administration. We hypothesized that an amino acid sequence mimicking the major heparin binding domain (HBD) of HL will displace HL from cell surfaces. To test this hypothesis, we generated a HL peptide that contains the amino acid sequence of the putative HBD of HL. The heparin binding of the peptide has been tested using heparin-sepharose and we demonstrate that it adsorbs and optimally elutes comparable to what we have also demonstrated with full length HL. We have also demonstrated that the peptide can displace HL from cell surfaces in vitro using HEK293 cells overexpressing HL. Since no portion of the HL structure is known, we are also conducting experiments to elucidate the structure of the major HBD of HL. This, in partnership with the functional analysis, should provide a novel understanding of the HBD of HL in affecting lipoprotein metabolism in vivo.