Activation of lipoprotein lipase by apolipoprotein C-II is modulated by the COOH terminal region of apolipoprotein C-III.
The in vitro effect of apolipoprotein C-II (apo C-II) on the apolipoprotein C-III (apo C-III) induced activation of bovine milk lipoprotein lipase ( LPL) was studied in vitro using a synthetic substrate. Apo C-III effectively inhibited, in a dose-dependent manner, the activation of lipoprotein lipase induced by apo C-II. A 3-fold molar apo C-III excess decreased the lipoprotein lipase activity by 25%. Thrombin cleavage of apo C-III produced two fragments: only fragment 41-79 retained the inhibitory activity and was equipotent to native apo C-III1 on a molar basis. Neither displacement of apo C-II from the substrate, as determined using 125I-labeled apo C-II, nor the charge carried by sialic residues of apo C-III, as demonstrated in experiments performed after neuraminidase treatment, accounted for this effect. I speculate that apo C-III may act by inhibiting the apo C-II- LPL interaction.[1]References
- Activation of lipoprotein lipase by apolipoprotein C-II is modulated by the COOH terminal region of apolipoprotein C-III. Catapano, A.L. Chem. Phys. Lipids (1987) [Pubmed]
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