Identification of Phoslactomycin E as a Metabolite Inducing Hyphal Morphological Abnormalities in Aspergillus fumigatus IFO 5840

Abstract

In our survey for antifungal compounds, a fermentation broth of Streptomyces sp. HA81-2 was found to inhibit the in vitro growth of Aspergillus fumigatus IFO 5840 accompanied by hyphal morphological abnormalities. One of the isolated antibiotics was identified as phoslactomycin E based on LC-MS and NMR spectral data. In a preliminary assay using the membrane fractions of A. fumigatus, phoslactomycin E was found to inhibit the activity of 1,3-b glucan synthase.Keywords antifungal activity, phoslactomycin E, Aspergillus fumigatus, hyphal morphological abnormalities, 1,3-b glucan synthase Opportunistic fungal infections are a major cause of serious morbidity and mortality in immunocompromised patients. However, there are few drugs for antifungal chemotherapy of deep-seated mycosis. As both human and fungal cells are eukaryotes, it is difficult to develop antifungal drugs without side effects in human hosts. Current targets are limited to ergosterol, cell wall components, biosynthetic pathways of cell wall and cytosine deaminase [1,2]. Therefore, there is a great need for novel antifungal drugs with new mechanisms of action. Morphological deformation of fungal hyphae is often induced by antifungal drugs [3]. As this phenomenon is specific to fungi, it could be used to screen for selective antifungal antibiotics [4]. In addition, this hyphal deformation is expected to reflect the disruption of cell wall biosynthesis, which is a specific target of antifungal agents. Moreover, investigating the mechanism of antifungal-induced hyphal morphological abnormalities is potentially useful for understanding the morphogenesis of fungal hyphae.In the course of our search for antifungal antibiotics, we found that a fermentation broth of Streptomyces sp. HA81-2 exhibited antifungal activity against Aspergillus fumigatus IFO 5840 accompanied by hyphal abnormalities. The isolated active fraction was identified as phoslactomycin E (PLME) [5] based on LC-MS and NMR spectral data. We herein report the isolation procedures for PLME, its molecular characteristics, and its induction of morphological changes in fungal cells.Active principles were isolated as follows; fermentation broth was filtered, the filtrate was applied on Diaion HP-20 column, and then eluted using an increasing gradient of aq MeOH (10ϳ100%). The 80ϳ90% MeOH fractions were concentrated in vacuo to afford crude extract, which was partitioned between water and CHCl 3 . Purification of

Lactomycins A–C, Dephosphorylated Phoslactomycin Derivatives that Inhibit Cathepsin B, from the Marine-derived Streptomyces sp. ACT232

“…Although the relative stereochemistry within the three partial structures was identical with that of leustroducsin H [ 9 ], due to the insulation by double bonds and the possible free rotation of the bond between C7 and C8, it was not possible to correlate the relative configurations between the partial structures nor assign that of C8 on the basis of the NOESY data. The NMR data of 1 was very close to those reported for phoslactomycins [ 10 , 11 , 12 , 13 ] and leustroducsins [ 14 , 15 ], except for those around C9 and C18, which were phosphorylated and esterified, respectively, in the latter compounds. The presence of an almost identical biosynthetic gene cluster with those previously reported for phoslactomycins (vide infra) suggests that the stereochemistry is shared between lactomycin A and phoslactomycins.…”

Effect of nagilactone E on cell morphology and glucan biosynthesis in budding yeast Saccharomyces cerevisiae

“…These results indicate that nagilactone E only acted on yeast cells during proliferation. These phenomena were frequently observed in the case of cell wall-affecting antifungal drugs including mainly echinocandins [22,25].…”

“…An assay for (1, 3)-β-glucan synthase in S. cerevisiae cells was performed according to the methods of Shedletzky et al [24] and Mizuhara et al [25] with slight modifications.…”

Synthetic Strategies Employed for the Construction of Fostriecin and Related Natural Products

“…222 Phoslactomycins also possess antifungal activity. 223 The remarkable biological activity of phoslactomycin has inspired genetic engineering of mutant strains for the production of phoslactomycins. 37,183,224–227 …”