Structure-activity relationship of cyclic pentapeptide malformins as fibrinolysis enhancers.
The formation of blood clots in blood vessels causes severe ischemic diseases such as cerebral infarction and myocardial infarction. While searching for microbial products that increase fibrinolytic activity using an in vitro fibrin degradation assay, we found malformin A1, a disulfide form of cyclo(-d-Cys-d-Cys-l-Val-d-Leu-l-Ile-), as an active compound. In this study, we synthesized malformin derivatives using a solid-phase peptide synthesis method and evaluated their fibrinolytic activity and cytotoxicity. Reduction of the disulfide bond and linearization of the cyclic peptide frame decreased the pro-fibrinolytic activity. Substitution of a branched-chain amino acid with lysine resulted in loss of activity. However, protection of the amino group in the lysine derivatives by the tert-butoxycarbonyl (Boc) group rescued the inactivity. Furthermore, the phenylalanine derivatives also exhibited a similar pro-fibrinolytic effect compared to malformin A1. These results suggest that the disulfide bond, the cyclic peptide frame, and the bulky hydrophobic side chains play a crucial role in the pro-fibrinolytic activity of malformin. The effective dose of the active derivatives for the in vitro fibrin degradation showed similar ranges (1-5μM), while the order of cytotoxic potency for the active derivatives was as follows: Phe-derivatives>BocLys-derivatives>malformin A1>reduced form. These results showed no correlation between pro-fibrinolytic activity and cytotoxicity, suggesting the possibility of the synthesis for non-toxic malformin derivatives possessing the activity.
Department of Biochemistry, Akita University Graduate School of Medicine, 1-1-1 Hondo, Akita 010-8543, Japan. Electronic address: ykoizumi@med.akita-u.ac.jp.
Yukio
Y
Koizumi
School of Pharmaceutical Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
Kenichiro
K
Nagai
Department of Applied Biological Science, Tokyo Noko University, 3-5-8 Saiwaicho, Fuchu, Tokyo 183-8509, Japan.
Keiji
K
Hasumi
Department of Biochemistry, Akita University Graduate School of Medicine, 1-1-1 Hondo, Akita 010-8543, Japan.
Keiji
K
Kuba
Department of Biochemistry, Akita University Graduate School of Medicine, 1-1-1 Hondo, Akita 010-8543, Japan.
Toshihiro
T
Sugiyama
D005342:Fibrinolysis / Q000187:drug effects*; D006801:Humans; D020128:Inhibitory Concentration 50; D010456:Peptides, Cyclic / Q000737:chemistry* / Q000494:pharmacology*; D013057:Spectrum Analysis / Q000379:methods; D013329:Structure-Activity Relationship; D020298:U937 Cells
D010456:Peptides, Cyclic; C001675:malformins
Cyclic peptide; Cytotoxicity; Disulfide bond; Fibrinolysis; Malformin; Solid-phase peptide synthesis