Effect of Desialylation of Human Very Low Density Lipoproteins on Their In Vitro Catabolism by Bovine Lipoprotein Lipase
Stoline, Anne Marie
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C-III, one of the apoproteins of very low density lipoproteins (VLDL) , exists in three principal isomorphic forms, which differ in sialic acid content. Apoprotein C-III (Apo C-III) modifies the apo C-II-activated lipolysis of VLDL by extrahepatic lipoprotein lipase (LPL). The effect of sialic acid on C-III metabolic function is unknown. This experiment was designed to assess the effect of desialylation (removal of sialic acid) of VLDL apoproteins on their in vitro catabolism by LPL. VLDL from five subjects were desialylated with neuraminidase, and labelled with dansyl 5-dimethylaminonaphthalene- 1-sulfonyl, a fluorescent probe. Using a recently-developed spectrofluorometric system, the catabolism of sialylated and desialylated VLDL by bovine LPL was monitored. Fluorescence increase measured over time with a continuous recorder reflected rate and extent of lipolysis. For this series of five subjects, desialylat10n had no effect on VLDL lipolysis by LPL. Mean initial lipolytic rates for neuraminidase-treated VLDL and native VLDL were both 10.2 units/min. F30/FO values, measuring the extent of lipolysis, were 4.1 units/min for both neuraminidase-treated VLDL and native VLDL. These results indicate that sialic acid does not affect VLDL as a substrate for catabolism by LPL in vitro.
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