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PubMed1983

[Antibacterial peptides (18). Synthesis and antibacterial activity of alpha-acyltetrapeptides containing basic amino acids (7)].

Three kinds of (formula; see text) were synthesized to investigate the relationship between the chemical structure and the antibacterial activities by acylation of the corresponding tetrapeptides. Acyl chlorides of (+)-6-Methyloctanoic acid (a component of colistin) and two kinds of other organic acid were employed as acylating agents. It was proved that one of three, (formula; see text) shows antibacterial activity against four kinds of Gram-negative bacteria and against Gram-positive bacteria, but that the other only have weak antibacterial activity.

Chemical Phenomena↗
PubMed1983

[Antibacterial peptides (XX). Synthesis and antibacterial activity of alpha-acyltetrapeptides containing basic amino acids (IX)].

In order to compare the antibacterial activity with Acyl-Lys-Lys(Thr)-Glu-OH (I), already reported, 3 kinds of Acyl-Lys-Lys(Glu)-Thr-OH (9a - c) and corresponding tetrapeptide (10), which were exchanged Thr for Glu on I, were synthesized by dicyclohexylcarbodiimide method. It was proved the (+)-6-methyloctanoyl-Lys-Lys(Glu)-Thr-OH (9a) shows antibacterial activity against 5 kinds of Gram-negative bacteria and against 2 kinds of Gram-positive bacteria, but that the others (9b), (9c), only have the weak one, and that tetrapeptide has against Gram-positive bacteria; and that those compounds have almost the same one as Acyl-Lys-Lys(Thr)-Glu-OH (I) has.

Amino Acids↗
PubMed1994

Identification of basic amino acid residues in thrombin essential for heparin-catalyzed inactivation by antithrombin III.

The therapeutically important anticoagulant heparin catalyzes inactivation of thrombin by antithrombin III via formation of an intermediary ternary thrombin-heparin-antithrombin III complex that is subsequently converted to a stable thrombin-antithrombin III complex with the release of heparin. Point mutations at Arg-180, Arg-245, Lys-248, and Lys-252 in thrombin markedly reduced the efficiency of heparin catalysis by decreasing the stability of the ternary intermediate, whereas the inactivation of thrombin by antithrombin alone was not affected by these mutations. These results together with an analysis of the x-ray crystal structure of thrombin yielded a model for the thrombin-heparin interaction, wherein heparin forms salt linkages along a groove in thrombin defined by Lys-252, Lys-248, Arg-245, Arg-89, Arg-98, and Arg-180.

Amino Acid Sequence↗