Biological and Pharmaceutical Bulletin
Online ISSN : 1347-5215
Print ISSN : 0918-6158
ISSN-L : 0918-6158
Characterization of Poly-Leucine Substituted Analogues of the Human Surfactant Protein SP-C
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1996 年 19 巻 12 号 p. 1550-1555


A series of novel amphipathic peptides constituted of an N-terminal hydrophilic portion (CPVHLKR, residues 6-12) of human pulmonary surfactant protein-C (SP-C) and a poly-leucine (poly-L) stretch of various chain lengths as the C-terminal hydrophobic tail were synthesized and evaluated relevant to their ability to improve the surface activity of a ternary lipid mixture composed of dipalmitoylphosphatidylcholine, egg-phosphatidylglycerol and palmitic acid (DPPC/E-PG/PA, 75 : 25 : 10, w/w) in a Langmuir-Wilhelmy surface balance. CPVHLKRL11, a human SP-C analogue bearing an 11-residue poly-L tail, and its related peptides with longer tails in the ternary lipid mixture, accelerated not only the surface spreading at the air-water interface but also exhibited significantly improved dynamic surface activity, compared to the ternary lipid mixture. Their surface activities were almost indiscernible from those of the synthetic human SP-C. When reconstituted into a ternary lipid mixture containing members of the homologous series of n-saturated diacylphosphatidylglycerol, the surface activities of the poly-L analogues were almost completely unaffected, whereas replica peptides carrying the hydrophobic portion of native SP-C were found to have distinct surface activities depending upon the acyl-chain lengths of phosphatidylglycerol. The poly-L stretch of a poly-L analogue could be replaced with poly-norleucine of the same chain length without a significant loss of surface activity.Substitution of the poly-L portion in the analogues with poly-valine or poly-isoleucine resulted in a considerable decrease in surface activity. The poly-L analogue in the DPPC/E-PG/PA mixture was demonstrated to act as an excellent surfactant comparable with Surfactan[○!R], a modified bovine surfactant preparation that was used for treatment for infant respiratory distress syndrome, based on evaluation of the lung pressure-volume characteristics using premature rabbit neonates.

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