Probestin, a new inhibitor of aminopeptidase M, produced by Streptomyces azureus MH663-2F6. II. Structure determination of probestin

Probestin, a new inhibitor of aminopeptidase M, has been isolated from the culture broth of Streptomyces azureus MH663-2F6. The 1H and 13C NMR studies and amino acid analysis confirmed the presence of one 3-amino-2-hydroxy-phenylbutanoic acid, leucine and two proline residues in the molecule. Stereochemistries of these amino acids were determined by HPLC analysis. The fragmentation pattern shown in the mass spectrum and the chemical analysis on probestin clarified the amino acid sequence. Thus the structure of probestin was defined as (2S,3R)-3-amino-2-hydroxy-4-phenylbutanoyl-L-leucyl-L-prolyl-L-pro line.