ESTABLISHMENT OF ENZYME-LINKED IMMUNOSORBENT ASSAYS FOR LIPOPROTEIN-LIPASE WITH NEWLY DEVELOPED ANTIBODIES

We developed eight new antibodies against lipoprotein lipase (LPL), wh ich included polyclonal antibodies raised against recombinant human LP L produced by transformant cells and two synthetic peptides correspond ing to either amino (N)- or carboxy (C)-terminus of human LPL. With th ese antibodies, we established three effective sandwich enzyme-linked immunosorbent assays (ELISAs) for LPL, which enabled us to examine LPL mass not only in the postheparin plasma from human, rat, mouse, and g uinea pig but also in the media and lysates of cultured cells. All of the developed antibodies showed high affinities for LPL, but their bin ding to LPL did not always influence the lipolytic activity of the enz yme. Interestingly, although the anti-C-terminus antibody should bind to a common epitope of human and mouse LPL, its binding selectively su ppressed only human LPL activity. Because amino acid sequence surround ing the epitope is common to both LPLs, difference in the sequence out side the epitope will contribute to the selective suppression of LPL a ctivity by the antibody. Our results also suggested that both termini of LPL would be exposed on the surface of the molecule because they we re fully accessible to antibodies and that the N-terminus of LPL would be functionally less important because binding of the anti-N-terminus antibody did not affect human LPL activity. The ELISAs were further u tilized to demonstrate the presence of C-terminus truncated LPL protei n in the postheparin plasma of an LPL-deficient patient, to map an epi tope of the anti-C-terminus antibody within residues 433-436, and to g ain insight into the structure-function relationship of the LPL molecu le. Availability of effective antibodies that have different epitope s pecificities and different inhibitory effects on LPL function will be of great use in immunological analysis of LPL.