Hayamitsu Adachi

Tripropeptin C Blocks the Lipid Cycle of Cell Wall Biosynthesis by Complex Formation with Undecaprenyl Pyrophosphate

ABSTRACT Tripropeptin C (TPPC) is a naturally occurring cyclic lipodepsipeptide antibiotic produced by a Lysobacter sp. TPPC exhibits potent antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and penicillin-resistant Streptococcus pneumoniae. This antibiotic also inhibits the incorporation of N-acetylglucosamine into the peptidoglycan of S. aureus at a 50% inhibitory concentration (IC50) of 0.7 μM, which is proportional to its MIC (0.87 μM; equivalent to 1.0 μg/ml). Treatment of exponential-phase S. aureus cells with TPPC resulted in accumulation of UDP-MurNAc-pentapeptide in the cytoplasm. The antimicrobial activity of TPPC was weakened by the addition of prenyl pyrophosphates but not by prenyl phosphates, UDP-linked sugars, or the pentapeptide of peptidoglycan. The direct interaction between TPPC and undecaprenyl pyrophosphate (C55-PP) was observed by mass spectrometry and thin-layer chromatography analysis, indicating that TPPC can potentially inhibit C55-PP phosphatase activity, which plays a crucial role in the lipid cycle of peptidoglycan synthesis. As expected, TPPC inhibits this enzymatic reaction at an IC50 of 0.03 to 0.1 μM in vitro, as does bacitracin. From the analysis of accumulation of lipid carrier-related compounds, TPPC was found to cause the accumulation of C55-PP in situ, leading to the accumulation of a glycine-containing lipid intermediate. This suggested that the TPPC/C55-PP complex also inhibits the transglycosylation step or flippase activity, adding to the inhibition of C55-PP dephosphorylation. This mode of action is different from that of currently available drugs such as vancomycin, daptomycin, and bacitracin.

THE STRUCTURE OF DIPHENAZITHIONIN, A NOVEL ANTIOXIDANT FROM STREPTOMYCES GRISEUS ISP 5236

A novel member of thephenazine group of metabolites, diphenazithionin, has been isolated as an inhibitor of lipid peroxidation from Streptomyces grisais ISP 5236. It possesses a unique structure composing of two different phenazinecarboxylic acids connected by a sulfur linkage.

Decalpenic acid, a novel small molecule from Penicillium verruculosum CR37010, induces early osteoblastic markers in pluripotent mesenchymal cells

Osteoblasts are the cells responsible for bone formation during embryonic development and adult life. Small compounds that could induce osteoblast differentiation might be promising sources of therapies for bone diseases such as osteoporosis. During screening for inducers of osteoblast differentiation of mouse pluripotent mesenchymal C3H10T1/2 cells, we isolated a small compound from the fermentation broth of Penicillium verruculosum CR37010. This compound, named decalpenic acid, bears a decalin moiety with a tetraenoic acid side chain. Treatment of C3H10T1/2 cells with decalpenic acid alone induced the expression of early osteoblast markers, such as alkaline phosphatase activity and osteopontin mRNA, but did not induce the late osteoblast marker osteocalcin mRNA or adipocyte markers under our experimental conditions.

Glycosidase inhibitors of gem-diamine 1-N-iminosugars: Structures in media of enzyme assays

The relationships between structures and inhibitory activities of glycosidase inhibitors of gem-diamine 1-N-iminosugars in media of enzyme assays have been investigated. It has been proved that gem-diamine 1-N-iminosugar smoothly undergoes a structural change to a hydrated ketone or its derivative via a hemiaminal in the media (pH 5.0-6.3), and that the products generated in the media as well as the parent gem-diamine 1-N-iminosugars potently inhibit glycosidases.

A New Type of Tripropeptin with Anteiso-branched Chain Fatty Acid from Lysobacter sp. BMK333-48F3

Branched chain amino acids are often utilized as the precursors of many lipid-containing bacterial secondary metabolites. The effect of isoleucine on the composition of the mixture of cyclic lipopeptide antibiotics, tripropeptins from Lysobacter sp. BMK333-48F3 was evaluated. As expected, a novel tripropeptin analog with an anteiso-branched fatty acid was produced. The new compound, TPPaiC shows potent antibacterial activity against Gram-positive bacteria including MRSA and VRE. On the other hand, no increase was observed in the production of other tripropeptins by the addition of isoleucine.

Amycolamicin: A Novel Broad‐Spectrum Antibiotic Inhibiting Bacterial Topoisomerase

The abuse of antibacterial drugs imposes a selection pressure on bacteria that has driven the evolution of multidrug resistance in many pathogens. Our efforts to discover novel classes of antibiotics to combat these pathogens resulted in the discovery of amycolamicin (AMM). The absolute structure of AMM was determined by NMR spectroscopy, X-ray analysis, chemical degradation, and modification of its functional groups. AMM consists of trans-decalin, tetramic acid, two unusual sugars (amycolose and amykitanose), and dichloropyrrole carboxylic acid. The pyranose ring named as amykitanose undergoes anomerization in methanol. AMM is a potent and broad-spectrum antibiotic against Gram-positive pathogenic bacteria by inhibiting DNA gyrase and bacterial topoisomerase IV. The target of AMM has been proved to be the DNA gyrase B subunit and its binding mode to DNA gyrase is different from those of novobiocin and coumermycin, the known DNA gyrase inhibitors.

Biological activities of pargamicin A, a novel cyclic peptide antibiotic from Amycolatopsis sp.

The time-kill studies using pargamicin A against Staphylococcus aureus and Enterococcus faecalis were performed. The effects of the incorporation of radioactive precursors into macromolecules, membrane potential and function using fluorescent dyes were also examined. These studies revealed that rapid bactericidal activity of pargamicin A correlates with the perturbation of bacterial cell membrane potential and membrane function.

Asteltoxins from the Entomopathogenic Fungus Pochonia bulbillosa 8-H-28

New asteltoxins C (3) and D (4) were found in the extract of the entomopathogenic fungus Pochonia bulbillosa 8-H-28. Compound 2, which was spectroscopically identical with the known asteltoxin B, was isolated, and structural analysis led to a revision of the structure of asteltoxin B. Compounds 2 and 4 have a novel tricyclic ring system connected to a dienyl α-pyrone structure. Compound 3 has a 2,8-dioxabicyclo[3.3.0]octane ring similar to that of asteltoxin (1). Compound 3 showed potent antiproliferative activity against NIAS-SL64 cells derived from the fat body of Spodoptera litura larvae, while 2 and 4 were inactive.

Synthesis and inhibitory activity of 8-substituted 2-deoxy-β-KDO against CMP-KDO synthetase

3-Deoxy-D-manno-octulosonate cytidyltransferase (CMP-KDO synthetase) is involved in the biosynthesis of lipopolysaccharide (LPS) which is an essential component of the outer membrane of gram-negative bacteria. New CMP-KDO synthetase inhibitors, 8-substituted derivatives of 2-deoxy-β-KDO (2) have been prepared. Compounds 8, 11, 15 and 16 in which the 8-hydroxyl group of 2 is replaced by guanidine, di(carbamoylethyl)amino, p-methoxy- or p-nitro-benzyloxycarbonylamino, respectively affect moderately the CMP-KDO synthetase activity.

Decalpenic acid induces early osteoblastic markers in pluripotent mesenchymal cells via activation of retinoic acid receptor γ.

Decalpenic acid is a natural small molecule previously isolated from the fermentation broth of fungi that induces early osteoblastic markers in pluripotent mesenchymal cells. Treatment of mouse pluripotent mesenchymal C3H10T1/2 cells with decalpenic acid gave rise to a morphological change similar to that induced by the treatment with retinoic acid, i.e. the cells adopted a more elongated spindle shape. Using a retinoic acid response element reporter and receptor activity assays, we show that decalpenic acid is a new retinoid with selectivity towards retinoic acid receptors γ and α. The induction of early osteoblastic markers by decalpenic acid was significantly inhibited by treatment with the retinoid antagonist, LE540, or with small interfering RNA-mediated knockdown of retinoic acid receptor γ. These results demonstrated that decalpenic acid induces early osteoblastic markers in pluripotent mesenchymal cells through activation of retinoic acid receptor γ.