Dual Carbamoylations on the Polyketide and Glycosyl Moiety by Asm21 Result in Extended Ansamitocin Biosynthesis

SummaryCarbamoylation is one of the post-PKS modifications in ansamitocin biosynthesis. A novel ansamitocinoside with carbamoyl substitution at the C-4 hydroxyl group of the N-β-D-glucosyl moiety was identified from the ansamitocin producer, Actinosynnema pretiosum. Through biotransformation, the carbamoyltransferase gene asm21 was suggested to be responsible for the carbamoylation of the glucosyl moiety. Three new derivatives without the backbone carbamoyl group were isolated from an asm21 mutant and characterized by NMR spectroscopy. Among them, 18-O-methyl-19-chloroproansamitocin was the major product and the preferred substrate for macrolactam C-7 carbamoylation by Asm21. However, Asm21 exhibited higher catalytic efficiency toward the glucosyl moiety. Furthermore, the dual carbamoylations and N-glycosylation were precisely demonstrated in vivo. This work represents the first biochemical characterization of an O-carbamoyltransferase performing dual actions on both a polyketide backbone and a glycosyl moiety during ansamitocin biosynthesis

Saturable Absorption and Modulation Characteristics of Laser with Graphene Oxide Spin Coated on ITO Substrate

The graphene oxide (GO) thin film has been obtained by mixture of GO spin coated on substrate of indium tin oxide (ITO). The experiment has shown that continuous-wave laser is modulated when the graphene oxide saturable absorber (GO-SA) is employed in the 1064 nm laser cavity. The shortest pulse width is 108 ns at the pump power of 5.04 W. Other output laser characteristics, such as the threshold pump power, the repetition rate, and the peak power, have also been measured. The results have demonstrated that graphene oxide is an available saturable absorber for 1064 nm passive Q-switching laser

In Depth Natural Product Discovery from the Basidiomycetes Stereum Species

Natural metabolites from microorganisms play significant roles in the discovery of drugs, both for disease treatments in humans, and applications in agriculture. The Basidiomycetes Stereum genus has been a source of such bioactive compounds. Here we report on the structures and activities of secondary metabolites from Stereum. Their structural types include sesquiterpenoids, polyketides, vibralactones, triterpenoids, sterols, carboxylic acids and saccharides. Most of them showed biological activities including cytotoxic, antibacterial, antifungal, antiviral, radical scavenging activity, autophagy inducing activity, inhibiting pancreatic lipase against malarial parasite, nematocidal and so on. The syntheses of some metabolites have been studied. In this review, 238 secondary metabolites from 10 known species and various unidentified species of Stereum were summarized over the last seven decades

Secondary Metabolites from the Nematode-Trapping Fungus <i>Dactylellina haptotyla</i> YMF1.03409

As a representative nematode-trapping fungus, Dactylellina haptotyla can capture and kill nematodes by producing traps, known as adhesive knobs. In this paper, the strain of D. haptotyla YMF1.03409 was studied by means of medium screening, fermentation, and purification and identification of crude extracts. Eighteen compounds were obtained from D. haptotyla YMF1.03409, including two new metabolites, nosporins C (1) and D (2). The known metabolites were identified to be 3-chloro-4-methoxybenzaldehyde (3), 3-chloro-4-methoxybenzoic acid (4), 2-chloro-1-methoxy-4-(methoxymethyl)benzene (5), 3-hydroxy-3-methyloxindole (6), nicotinic acid (7), succinic acid (8), 3,4-dihydroxybutanoic acid (9), 5′-O-methyladenosine (10), uridine (11), 2′-deoxyuridine (12), thymidine (13), 3-(phenylmethyl)-2,5-morpholinedione (14), methyl-β-D-glucopyranoside (15), 1,2-benzenedicarboxylic acid bis(2-methyl heptyl) ester (16), β-sitosterol (17), and 3β,6α-diol-stigmastane (18). The bioactive assay showed that these compounds had no obvious nematicidal activity against the nematodes Meloidogyne incognita and Panagrellus redivivus

Secondary Metabolites from the Endoparasitic Nematophagous Fungus Harposporium anguillulae YMF 1.01751

Harposporium anguillulae, an endoparasitic nematophagous fungus (ENF), is a model fungus from which the genus Harposporium was established. It can infect nematodes via ingested conidia. In this paper, the morphology and nematode&ndash;fungus interaction between Panagrellus redivivus and H. anguillulae were observed by scanning electron microscopy (SEM). The secondary metabolites of H. anguillulae were also studied. Seven metabolites were purified and identified from an ethyl acetate extract of broth and a methanol extract of mycelium. These include a new polyketone 5-hydroxy-3-(hydroxymethyl)-6-methyl-2H-pyran-2-one (1) and six known metabolites (17R)-17-methylincisterol (2), eburicol (3), ergosterol peroxide (4), terpendole C (5), (3&beta;,5&alpha;,9&beta;,22E)-3,5-dihydroxy-ergosta-7,22-dien-6-one (6), and 5&alpha;,6&beta;-epoxy-(22E,24R)-ergosta-8,22-diene- 3&beta;,7&alpha;-diol (7). These metabolites were assayed for their activity against plant root-knot nematode, Meloidogyne incognita, and the results showed that terpendole C (5) had weak nematicidal activity but also that other compounds did not have evident activity at a concentration of 400 &mu;g mL&minus;1. Compound 1 exhibited an attractive effect towards P. redivivus