Kalafungin

Medermycin and kalafungin, two antibacterial and antitumor antibiotics isolated from different streptomycetes, share an identical polyketide skeleton core. The present study reported the discovery of kalafungin in a medermycin-producing streptomycete strain for the first time. A mutant strain obtained through UV mutagenesis showed a 3-fold increase in the production of this antibiotic, compared to the wild type strain. Heterologous expression experiments suggested that its production was severely controlled by the gene cluster for medermycin biosynthesis. In all, these findings suggested that kalafungin and medermycin could be accumulated by the same streptomycete and share their biosynthetic pathway to some extent in this strain.

A general, efficient, and common strategy for the synthesis of (-)-juglomycin A, (+)-kalafungin, (+)-frenolicin B, and (+)-deoxyfrenolicin is reported here. The strategy involves the synthesis of a key building block alkyne from a cheap chiral pool material, D-glucono-δ-lactone, Dötz benzannulation, oxa-Pictet-Spengler reaction, and H(2)SO(4)-mediated epimerization.

β-lactamase inhibitors are potent synergistic drugs to deteriorate the multidrug-resistant bacteria. Here, we report the β-lactamase inhibitory ability of kalafungin isolated from a marine sponge derived Streptomyces sp. SBRK1. The IC50 value of the kalafungin was calculated as 225.37 ± 1.95 μM against β-lactamase. The enzyme kinetic analysis showed the Km value of 3.448 ± 0.7 μM and Vmax value of 215.356 ± 8 μM/min and the inhibition mechanism was identified as uncompetitive type. Along with the antibacterial activity, the cell surface analysis of kalafungin treated Staphylococcus aureus cells revealed destruction of cell membrane in response to β-lactamase inhibition. Molecular docking studies have confirmed the binding property of kalafungin against β-lactamase with two hydrogen bonds. In vivo efficacy studies in the zebrafish model by green fluorescent protein expressing S. aureus infection, survival, safety and behavioral profile were reported. The toxicity and anti-infection revealed that the compound was evidently active and safe to all organs. In conclusion, this is the first report on kalafungin with β- lactamase inhibition and suggests that kalafungin may useful for synergic antibacterial therapy with β-lactam drugs to overcome β-lactamase-based resistance of any bacterial pathogens.