In a previous study, CETP inhibitory peptide (3 kDa) was isolated from hog plasma. The peptide, synthesized chemically according
to the amino acid sequence of the 3-kDa peptide (designated P
28), showed CETP inhibitory activity both
in vitro and
in vivo [Cho
et al. (1998)
Biochim. Biophys. Acta 1391, 133–144]. We report herein further unique features of P
28 when it was associated with the cholesteryl ester (CE)-donor and-acceptor lipoproteins. Lipoprotein substrates with P
28 present in both HDL (as a CE-donor) and LDL (as a CE-acceptor) served as poor substrates, with CE-transfer activity decreased
up to 60% compared to normal substrates without P
28. P
28 was found to be located in HDL fractions of hog plasma and showed the same electromobility as that visualized by PAGE on
7% polyacrylamide gel under nondenaturing conditions. Addition of apolipoprotein A-1 (apoA-1) or apoB antibody to a normal
CE-transfer mixture did not alter CE-transfer activity. However, addition of apoA-1 or −B antibody to a CETP-inhibition mixture
decreased the inhibitory activity of P
28 by
ca. 20%. Western blot analysis revealed that P
28 was associated only with human and hog HDL among several lipoproteins purified from human, hog, and rabbit. CFTP-inhibition
assays with various lipoprotein substrates revealed that P
28 exhibited substrate-specific inhibitory activity. The inhibitory activity of P
28 was highly dependent on the type of lipoprotein substrate (whether CE-donor or-acceptor); P
28 inhibited CE transfer from HDL to LDL, but it did not inhibit CE transfer from HDL to HDL.
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