Nobuo Izumiya

Relationship between antimicrobial activity and amphiphilic property of basic model peptides

Several cationic model peptides of the prepiece moieties of mitochondrial protein precursors were found to be active against Gram-positive bacteria, but inactive against Gram-negative bacteria. The CD spectra of the model peptides in the presence of phospholipid liposomes demonstrated that antimicrobial activity was generally in parallel with the content of the alpha-helical amphiphilicity. The results indicate that appropriate positioning of cationic and hydrophobic groups in the stable alpha-helical structure of the peptides is important to exhibit antimicrobial activity. These peptides also have an ability to leak carboxyfluorescein from acidic and neutral phospholipid vesicles, suggesting that the peptides interact with the bacterial membrane to perturb it.

Action of trypsin on synthetic substrates: III. Hydrolysis of homologous peptides ranging from diglycyl-l-lysyl-glycine to diglycyl-l-lysyl-tetraglycine

Abstract A number of diglycyl- l -lysyl-(glycine) n , where n is 1, 2, 3, or 4, have been synthesized, and their susceptibility to the hydrolytic action of trypsin has been determined. Paper Chromatographic analyses of the incubation mixture proved that the substrates are subjected to simple hydrolysis at the peptide bond of lysylglycyl sequence. By comparison of the proteolytic coefficients, it was shown that the order of susceptibility to hydrolysis is diglycyllysyl-triglycine > -tetraglycine > -diglycine ⪢ -glycine.

Facile synthesis of Gramicidin S via cyclication of a linear pentapeptide

Abstract Azide and N -hydroxysuccinimide ester of five pentapeptides related to gramicidin S (cyclic decapeptide) were cyclized to determine the ratio of dimer to monomer in the cyclization product, the pentapeptide derivative with D-Phe as C -terminus giving the dimer in good yield.

Synthesis of a peptide with cobrotoxin activity

Abstract A peptide with the sequence of cobrotoxin was prepared by Merrifields solid-phase method. The peptide obtained was found to show similar behavior to natural cobrotoxin in an immunodiffusion experiment and to effect the response to acetylcholine of frog muscle. Further purification of this peptide raised the toxic activity up to about 20% of that of cobrotoxin.

Syntheses of antibacterial peptides, gramicidin S analogs and designed amphiphilic oligopeptides

Abstract In order to clarify the relationship between antimicrobial activity and peptide-structure, gramicidin S analogs and cationic α-helical model peptides were designed and synthesized. Introduction of cationic side chains in hydrophilic side of gramicidin S increased antimicrobial activity against Gram-negative bacteria. Amphiphilic structures of the α-helical peptides were found to be effective to show antimicrobial activities against Gram positive bacteria. Increase in number of cationic amino acid residues in the α-helical peptides caused appreciable antimicrobial activities against Gram-negative bacteria, however, induced lower activities against Gram-positive ones.

δ and μ opiate receptor probes: fluorescent enkephalins with high receptor affinity and specificity

The fluorescent amino acid, L‐1‐pyrenylalanine (Pya) was incorporated into [D‐Ala2,Leu5]enkephalin and its methyl ester at position 4 or 5. Pya‐enkephalins showed strong fluorescent intensity and displayed high binding affinity for opiate receptors. Pya4‐enkephalins showed high specificity for the μ receptors, while Pya5‐enkephalins showed high specificity and selectivity for the δ receptors. Particularly, [D‐Ala2,Pya5]enkephalin was as potent as the most utilized δ‐specific ligand of [D‐Ala2,D‐Leu5]enkephalin (DADLE), and yet its δ‐selectivity was about 5‐times greater than that of DADLE. Thus, Pya‐enkephalins per se can be utilized as a fluorescent probe or tracer for the opiate receptor‐binding assays.

Efficient asymmetric synthesis of α-amino acids through hydrogenation of α,β-dehydroamino acid residue in cyclic dipeptides

Abstract A series of cyclo (Δaminoacyl-L-Ala) ( 4 ) (Δ=α,β-dehydro) were prepared from cyclo(Gly-L-Ala) and corresponding aldehyde, and hydrogenated with Pd black in MeOH. Chiral inductions producing cyclo (L-aminoacyl-L-Ala) ( 5 ) from 4 were 96–99% in the case of L-Aba (2-aminobutanoic acid), L-Val, L-Leu, and L-App (2-amino-5-phenylpentanoic acid) as an L-aminoacyl moiety in 5 . Pure L-Leu, L-Aba, and L-App were synthesized in preparative scale from corresponding 4 through asymmetric hydrogenation and acid-hydrolysis.

Environment-dependent conformation and antimicrobial activity of a gramicidin S analog containing leucine and lysine residues

An analog of gramicidin S, cyclo(‐L‐Leu‐L‐Lys‐L‐Leu‐D‐Leu‐L‐Leu‐)2, in which four out of five amino acid components of gramicidin S were substituted, has been synthesized. This analog assumes a conformation similar to that of gramicidin S in acidic liposomes and a random conformation in neutral liposomes. The antimicrobial activity of this analog corresponded to one‐fourth of that of gramicidin S. A possible mechanism for conformational changes in acidic liposomes is discussed.

Synthesis and activity of nonapeptide fragments of soybean Bowman-Birk inhibitor

Zwei Nonapeptidfragmente des Bowman-Birk Inhibitors wurden mit Hilfe der Merrifield-Synthese hergestellt und deren Trypsinhemmende Aktivität bestimmt.

Anti-chymotrypsin and anti-elastase activities of a synthetic bicyclic fragment containing a chymotrypsin-reactive site of soybean Bowman-Birk inhibitor

A bicyclic hexadecapeptide, which corresponds to the sequence 36-51 and contains the chymotrypsin-reactive Leu-43-Ser-44 bond of soybean Bowman-Birk inhibitor, has been synthesized. This peptide consists of two loops formed by disulfide bridges between Cys-36 and Cys-51 and between Cys-41 and Cys-49. The bicyclic peptide showed a strong anti-chymotryptic activity with a Ki of 7.1.10(-7) M. Comparison of inhibitory activity and digestive stability against chymotrypsin with other hexadecapeptides having the same sequence but lacking one or both disulfide bridges suggested that the compact bicyclic structure increases the activity and protects the Leu-Ser bond from chymotryptic digestion. Interestingly, the bicyclic peptide was found to inhibit porcine pancreatic elastase with a Ki of 4.3.10(-5) M, indicating the broad specificity of this ring system.