LIPOLYSIS OF VERY-LOW-DENSITY LIPOPROTEINS BY HEPARAN-SULFATE PROTEOGLYCAN-BOUND LIPOPROTEIN-LIPASE

An in vitro assay to study lipolysis of very low density lipoproteins (VLDL) by heparan sulfate proteoglycan (HSPG-bound lipoprotein lipase (LPL) was developed. Optimal conditions for VLDL lipolysis by HSPG-bou nd LPL were obtained by incubating plastic wells with 0.5 mu g HSPG an d 1.5 mu g LPL, subsequently. Control experiments with heparinase indi cate that at least 90% of the LPL activity is derived from LPL bound t o heparan sulfate chains. For HSPG-LPL-mediated lipolysis, the apparen t K-m and V-max values were 0.36 +/- 0.11 mM VLDL-triglycerides and 1. 2 +/- 0.1 mu M free fatty acids/min.ng LPL, respectively. The mean int ra-assay and inter-assay coefficients of variance were 5% and 8%, resp ectively.