Calpinactam is a fungal hexapeptide active against Mycobacterium species.
Details
Calpinactam is a fungal hexapeptide metabolite isolated from Mortierella alpina FKI-4905. Structurally, it contains a unique C-terminal caprolactam ring and was characterized by detailed NMR analysis and total synthesis. Calpinactam exhibits selective antimycobacterial activity, inhibiting the growth of Mycobacterium smegmatis and Mycobacterium tuberculosis with low-micromolar MIC values while showing minimal activity against other bacteria and fungi. Biosynthetic studies revealed that calpinactam is produced by a large nonribosomal peptide synthetase (NRPS), and heterologous expression systems have enabled its production from long fungal biosynthetic genes.