0Location:
Walls of blood capillaries, anchored to the endothelium by negatively charged proteoglycan chains of heparan sulfate.
Tissue distribution:
Heart, adipose tissue, spleen, lung, renal medulla, aorta, diaphragm, and lactating mammary gland
It is not typically found in blood; lipoprotein lipase is released from its heparan sulfate binding sites into the circulation following injection of heparin.
Activators and inhibitors:
Phospholipids and apo C-II are required as cofactors for lipoprotein lipase activity
Apo A-II and apo C-III act as inhibitors
Action:
It hydrolyses the triglycerides in chylomicrons and VLDL to form their corresponding remnants. Hydrolysis takes place while the lipoproteins are attached to the enzyme on the endothelium. Triacylglycerol is hydrolysed progressively through a diacylglycerol to a monoacylglycerol and finally to free fatty acids and glycerol.
Hormonal regulation:
Nor-epinephrine liberated from sympathetic nerve endings increases lipolysis in the tissues and increases synthesis of lipoprotein lipase.
In adipose tissue and skeletal muscle, extracellular lipoprotein lipase is synthesised and activated in response to insulin.
Defect:
Familial lipoprotein lipase deficiency (type I) – There is a slow clearance of chylomicrons and VLDL which leads to hypertriacylglycerolemia. It may also occur due to apo C-ll lack. Clinical features are pancreatitis, xanthomas.
