Unguisin C, a GABA-containing cyclic peptide from the fungus Emericella unguis

• Published in: Phytochemistry (Oxford) Vol. 60; no. 8; pp. 869 - 872
• Main Authors: Malmstrøm, Joan, Ryager, Anne, Anthoni, Uffe, Nielsen, Per Halfdan
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier Ltd 01.08.2002; Elsevier
• Subjects: Bacteriology; Biochemistry & Molecular Biology; Biological and medical sciences; Cyclic peptides; Emericella - chemistry; Emericella unguis; Fundamental and applied biological sciences. Psychology; Fungus; GABA; gamma-Aminobutyric Acid - chemistry; Life Sciences & Biomedicine; Microbiology; Morphology, structure, chemical composition; Peptides, Cyclic - chemistry; Peptides, Cyclic - isolation & purification; Plant Sciences; Protein Conformation; Science & Technology; Spectrum Analysis; Unguisin C; Unguisin D; GABA; Fungus; Emericella unguis; Cyclic peptides; Unguisin D; Unguisin C; cyclic peptides; METABOLITES; fungus; unguisin c; unguisin D; Fungi; Culture medium; Molecular structure; Aminoacid; Isolation; Ascomycetes; Biosynthesis; Heptapeptide; Stereochemistry; Thallophyta
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/S0031-9422(02)00150-4

Besides the known unguisins A and B, a new cyclic heptapeptide, unguisin C, containing a GABA-derived moiety in the ring, was isolated from the fungus Emericella unguis. The structure was determined by 1D and 2D NMR techniques. Marfey's method was used to determine the absolute stereochemistry. Precursor-directed biosynthesis of the unguisins was performed by supplementation of the culture medium with amino acids ( l-Ala, l-Ser, l-Phe and l-Leu). A related cyclic heptapeptide, unguisin D, was detected by HPLC and characterized by sequence analysis using LC-QITMS. Unguisin C was isolated from the fungus Emericella unguis. As in the previously identified unguisines A and B, a GABA-derived moiety was incorporated in a cyclic heptapeptide. Precursor-directed synthesis indicated conservation of the common key substructure Trp-GABA-Ala-Val in all the cyclic heptapeptides produced.