Lecithin: cholesterol acyl transferase (LCAT).

Esterification of cholesterol in plasma is mediated by LCAT. The mechanism of the three reactions catalysed by the enzyme is beginning to be understood. LCAT has been purified from human plasma and partially characterized. The enzyme is closely associated with HDL and exists most likely as a complex with its activator apo A-I and apo D. Antibodies were raised against LCAT and the enzyme concentration in plasma has been estimated to range between 4.5 and 8.0 mg/L. In patients with familial LCAT deficiency only trace amounts or no LCAT protein is found. Heterozygotes for this disorder have approximately half the normal amount of the enzyme. LCAT reactivity is essential for normal lipoprotein metabolism and for a proper equilibrium between tissue and plasma cholesterol.