Apolipoprotein C-II Deficiency
The lipolysis of chylomicrons and very low density lipoproteins is responsible for the delivery of energy in the form of fatty acids to adipose or muscle tissue. The fatty acids are transported in the form of triacylglycerols in these lipoproteins following their synthesis in the intestine or liver. Defects in this process result in massive accumulations of triacylglycerols in plasma. A deficiency of lipoprotein lipase, the major enzyme responsible for the hydrolysis of lipoprotein triacylglycerols in peripheral tissues, was recognized (1) over 20 years ago as one cause of hyperchylomicroneraia. Subsequently (2,3) the specific plasma component necessary for normal lipoprotein lipase activity was isolated from very low density lipoproteins (VLDL) and identified as apolipoprotein C-II (apo C-II). The apolipoprotein, which contains 79 amino acids, influences lipoprotein lipase activity by reducing the Km of the enzyme for triacylglycerol emulsions (4) or apo C-II deficient VLDL (5,6). In one instance apo C-II also increased the Vmax of the reaction (6).
KeywordsLipoprotein Lipase Hepatic Lipase Lecithin Cholesterol Acyl Transferase Isoelectric Focussing Obligate Heterozygote
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