Heparan sulphate and the binding of lipoprotein lipase to porcine thoracic aorta endothelium.

Purified bovine milk lipoprotein lipase was shown to bind to intact porcine aortic endothelium in a specific, saturable fashion. The binding was reversed by exogenous heparin. A single class of binding sites was involved and at saturation 1.24 x 10(11) molecules of lipoprotein lipase/cm2 were bound. This represents 0.51 x 10(6) enzyme molecules per endothelial cell at a density of 1.2 x 10(3) molecules/micrometers 2. The enzyme binding was reduced by prior trypsinisation of the endothelial surface under conditions that removed cell surface glycosaminoglycan chains. The porcine endothelium was shown to have available at its surface 5.4 x 10(11) chains of heparan sulphate plus heparin-like glycosaminoglycans/cm2. Such an excess suggests that lipoprotein lipase may interact with approximately one in four of the available heparan sulphate chains.