Kosaku Noda

Synthesis of cyclotetrapeptides, am-toxin analogs, containing α-hydroxyalanine

Abstract Condensation of amide with α-keto acid to yield a α-hydroxyalanine (α-Hyala) or dehydroalanine residue was applied to syntheses of analogs of AM-toxins, cyclotetradepsipeptides. Cyclo (-α-Hyala-L-Ala-L-Val-L-Phe-), cyclo (-α-Hyala-L-Ala-L-Hmb-L-Phe-) and cyclo (-α-Hyala-L-Ala-L-Hmb-L-Tyr-) (Hmb, 2-hydroxy-3-methylbutanoic acid) were obtained from the corresponding pyruvyl-tripeptide amides in good yields by the treatment of anhydrous hydrogen fluoride.

Electrochemical behavior of copper(II)-dipeptide complexes in mixed solvents

Abstract Several copper(II)-dipeptide complexes were investigated in water-solvent (acetonitrile, N , N - dimethylformamide and dimethylsulfoxide) mixtures by electrochemical methods. The effects of the solvents on the reduction potentials of the copper- (II) dipeptide complexes were discussed. The reduction potentials in mixed solvents were different from those in aqueous solution and the order of reduction potentials was found to be due to the functional groups of the amino acid residue of the peptides in spite of quasi-reversible electrode reactions for the complexes.

Syntheses of AM-toxin III and its analogs using the Hofmann degradation

Abstract Syntheses of cyclotetradepsipeptides, AM-toxin III and two analogs, were achieved, in which the Hofmann degradation method was used in order to derive a dehydroalanine residue from a 2,3-diaminopropionic acid residue in cyclodepsipeptide precursors.

Purification and characterization of a new serine proteinase from Bacillus subtilis with specificity for amino acids at P1 and P2 positions

A proteinase was purified 230-fold to apparent homogeneity from culture filtrates of Bacillus subtilis by a series of column chromatographies on DE52, DEAE-Toyopearl, Cellulofine GC200M, and Mono-Q, using Boc-Ala-Ala-Pro-Ser-pNA as a substrate. The molecular weight of the proteinase was estimated to be 42,000 by SDS-PAGE in the presence of 2-mercaptoethanol. Studies on the substrate specificity with peptide p-nitroanilides and natural peptides revealed that this proteinase preferentially hydrolyzed the peptide bond on the carboxyl-terminal side of either serine or alanine residues at the P1 position and hydrophobic bulky amino acids at P2. It was most active at pH 9.5 for the hydrolysis of Boc-Ala-Ala-Pro-Ser-pNA. The enzyme was inactivated by diisopropyl fluorophosphate (DFP), but not by tosyl-L-phenylalanine chloromethylketone (TPCK) or by EDTA. Based on the reactivity toward substrates and inhibitors, this enzyme differs from elastase- or subtilisin-like proteinase, hence it is a new type of proteinase with specificity for amino acids at P1 and P2 positions.