K. Polzhofer
1972
Citations
0
Influential Citations
17
Citations
Journal
Tetrahedron
Abstract
Abstract The solid phase synthesis of the pentadecapeptide H-Lys-His-Pro-Pro-His-Leu-Ser-Phe-Met-Ala-Ile-Pro-Pro-Lys-Lys-OH, 1 a partial peptide sequence from bovine -casein, is described. During the synthesis the N α -amino group of the individual amino acids was blocked by the t-butyloxycarbonyl residue (Boc), the N e -amino group of Lys by the benzyloxycarbonyl residue (Z). the OH group of Ser by the benzyl residue and the imidazole nitrogen of His by the 2,4-dinitrophenyl group. The stepwise condensation of the protected amino acids on to the peptidyl resin proceeded by means of the carbodiimide method. After the separation of the peptide from the carrier resin with purified HBr/Anisol with simultaneous cleavage of the benzyloxycarbonyl and benzyl protective groups, impure dinitrophenyl peptide hydrobromide was obtained in 59·8% yield calc. on the content of Lys in the Boc-Lys(Z)-polymer. The dinitrophenyl groups could be eliminated quantitatively in aqueous solution at pH 8 with 2-mercaptoethanol within 16 h. After purification of the peptide by gel chromatography on Sephadex G-25 in 0·05 M acetic acid, 13·6% of pure pentadecapeptide acetate were obtained. The purity was controlled by TLC in different solvent systems, by thin-layer electrophoresis and by quantitative amino acid analyses. The following peptides were synthesised by the same method for comparison: the octapeptide H-Lys-His-Pro-Pro-His-Leu-Ser-Phe-OH, the heptapeptide H-Met-Ala-Ile-Pro-Pro-Lys-Lys-OH, the hexapeptide H-His-Leu-Ser-Phe-Met-Ala-OH and the pentapeptides H-Leu-Ser-Phe-Met-Ala-OH and H-Ser-Leu-Phe-Met-Ala-OH. The pentadecapeptide is quantitatively split by rennin between Phe and Met at pH 4·25. The Michaelis-Menten constant for this reaction is 0·45 mmoles/l. The hexapeptide is also split by rennin whereas both pentapeptides were found to be resistant to rennin. The His residues in the peptides thus may be considered to be substrate specific. The pentadecapeptide and the hexapeptide as synthetic substrates are suitable for activity determinations and for a control of rennin preparations.