THE MUTANT ASN(291)-]SER HUMAN LIPOPROTEIN-LIPASE IS ASSOCIATED WITH REDUCED CATALYTIC ACTIVITY AND DOES NOT INFLUENCE BINDING TO HEPARIN

Lipoprotein lipase (LPL) plays a central role in triglyceride metaboli sm, regulating the catabolism of triglyceride-rich lipoprotein particl es, LPL performs its hydrolytic action attached to heparan sulfate pro teoglycans at the luminal surface of capillary endothelial cells, We h ave assessed the effect of the Asn(291) --> Ser (N291S) substitution f ound in LPL gene from a human hyperlipemic patient, Our results showed that both the wild-type (WT) and N291S hLPL expressed in COS1 cells w ere secreted to the extracellular medium, and presented similar intrac ellular distibution patterns, Furthermore, heparin-Sepharose affinity chromatography assays revealed normal heparin affinity of the N291S hL PL, In addition, both the mutant and the WT protein bound to the surfa ce of human fibroblasts and untransfected COS1 cells, Interestingly, d isminished LPL specific activity was observed in the extracellular med ium from mutant expressing cells, Therefore the lack of normal LPL act ivity in patients harbouring such a mutation could be the cause of the ir hyperlipemic disorder.