Polyene Amides Research Articles

The pcsA gene from Streptomyces diastaticus var. 108 encodes a polyene carboxamide synthase with broad substrate specificity for polyene amides biosynthesis

Two structurally related polyene macrolides are produced by Streptomyces diastaticus var. 108: rimocidin (3a) and CE-108 (2a). Both bioactive metabolites are biosynthesized from the same pathway through type I polyketide synthases by choosing a starter unit either acetate or butyrate, resulting in 2a or 3a formation, respectively. Two additional polyene amides, CE-108B (2b) and rimocidin B (3b), are also produced "in vivo" when this strain was genetically modified by transformation with engineered SCP2*-derived vectors carrying the ermE gene. The two polyene amides, 2b and 3b, showed improved pharmacological properties, and are generated by a tailoring activity involved in the conversion of the exocyclic carboxylic group of 2a and 3a into their amide derivatives. The improvement on some biological properties of the resulting polyenes, compared with that of the parental compounds, encourages our interest for isolating the tailoring gene responsible for the polyene carboxamide biosynthesis, aimed to use it as tool for generating new bioactive compounds. In this work, we describe the isolation from S. diastaticus var. 108 the corresponding gene, pcsA, encoding a polyene carboxamide synthase, belonging to the Class II glutamine amidotransferases and responsible for "in vivo" and "in vitro" formation of CE-108B (2b) and rimocidin B (3b). The fermentation broth from S. diastaticus var. 108 engineered with the appropriate pcsA gene construction, showed the polyene amides to be the major bioactive compounds.

Crucial Structural Factors and Mode of Action of Polyene Amides as Inhibitors for Mitochondrial NADH−Ubiquinone Oxidoreductase (Complex I)

Natural antibiotic polyene amides such as myxalamides are potent inhibitors of mitochondrial complex I. Because of the significant instability of this series of compounds due to an extended pi-conjugation skeleton, a detailed characterization of their inhibitory action has not been performed. To elucidate the action mechanism as well as binding manner of polyene amides with complex I, identification of the roles of each functional group in the inhibitory action is needed. We here synthesized a series of amide analogues and carried out structure-activity studies with bovine heart mitochondrial complex I. With respect to the left-hand portion, the natural pi-conjugation skeleton common to many natural products is not required for the inhibition and can be substituted with a simpler substructure such as a conjugated diene. The geometry and shape of the left-hand portion were shown to be important for the inhibition, suggesting that this portion may bind to a narrow hydrophobic pocket in the enzyme rather than merely partitioning into the lipid membrane phase. Concerning the right-hand portion of the inhibitor, the presence of the 2-methyl, amide NH, and (S)-1'-methyl groups was crucial for the activity, suggesting that both methyl groups neighboring the amide group finely adjust the hydrogen-bonding ability of the amide group. In contrast, modifications of the 2'-OH group did not significantly influence the activity, suggesting that the role of this functional group is not to serve as a hydrogen bond donor to the enzyme but to act as a hydrophilic anchor directing the right-hand portion at or near the membrane surface. Detailed characterization of the action mechanism indicated that the polyene amides share a common binding domain with other complex I inhibitors, though their binding position (or manner) within the domain may differ considerably from that of other inhibitors.

Zooxanthellamide D, a Polyhydroxy Polyene Amide from a Marine Dinoflagellate, and Chemotaxonomic Perspective of the Symbiodinium Polyols

A long-chain polyhydroxy polyene amide, zooxanthellamide D (ZAD-D, 1, C54H83NO19), was isolated from a cultured marine dinoflagellate of the genus Symbiodinium. ZAD-D (1) is a polyhydroxy amide consisting of a C22-acid part and a C32-amine part and furnishes three tetrahydropyran rings and six isolated butadiene chromophores. The relative stereochemistry of the tetrahydropyran ring systems was elucidated by NMR techniques. This metabolite showed moderate cytotoxicity against two human tumor cell lines. A phylogenetic tree of Symbiodinium has been updated and compared with the structures of the hitherto isolated polyols of Symbiodinium, zooxanthellatoxins and zooxanthellamides, providing a promising chemotaxonomic perspective for the classification of this morphologically indistinguishable dinoflagellate.

Selective activity of polyene macrolides produced by genetically modified Streptomyces on Trypanosoma cruzi

The growth inhibitory effects on Trypanosoma cruzi of several natural tetraene macrolides and their derivatives were studied and compared with that of amphotericin B. All tetraenes strongly inhibited in vitro multiplication. Proliferation of epimastigotes was arrested by all these drugs at ≤3.6 μM, which were also active on amastigotes proliferating in fibroblasts. Compared with amphotericin B, the compounds were less effective but also less toxic, showing no effect on the proliferation of J774 and NCTC 929 mammalian cells at concentrations active against the parasites. CE-108B (a polyene amide) appeared to be an especially potent trypanocidal compound, with strong in vivo trypanocidal activity and very low or no toxic side effects, and thus should be considered for further studies.

A Tailoring Activity Is Responsible for Generating Polyene Amide Derivatives in Streptomyces diastaticus var. 108

We recently characterized rimocidin B (3b) and CE-108B (4b) as two polyene amides with improved pharmacological properties, produced by genetically modified Streptomyces diastaticus var. 108. In this work, genetic and biochemical analysis of the producer strain show that the two amides are derived from the parental polyenes rimocidin (3a) and CE-108 (4a) by a post-PKS modification of the free side chain carboxylic acid. This modification is mediated by an amidotransferase activity operating after the biosynthesis of rimocidin (3a) and CE-108 (4a) are completed. Two polyenes, intermediates of the biosynthetic pathway of rimocidin (3a) and CE-108 (4a), were also isolated and shown to have some improved pharmacological properties compared with the final products.

Generating Novel Polyene Antifungal Drugs

In this issue of Chemistry & Biology, Francisco Malpartida and colleagues [1] report the formation of novel polyene amide derivatives upon transformation of the producer strain with SCP2*-derived vectors carrying the erythromycin resistance gene ermE. This unexpected finding provides a new tool for generating antifungal drugs by biotransformation.

Two Polyene Amides Produced by Genetically Modified Streptomyces diastaticus var. 108

Streptomyces diastaticus var. 108, a newly isolated strain, was recently characterized as a producer of two polyene macrolide antibiotics (rimocidin and CE-108), and the biosynthetic gene cluster was partially characterized. When the producer strain was genetically modified by transformation with some engineered SCP2*-derived vectors carrying the ermE gene, two previously uncharacterized macrolides were detected in the fermentation broth of the recombinant strain and chemically characterized as the amides of the parental polyene carboxylic acids. The biological activity and some in vitro toxicity assays showed that this chemical modification resulted in pharmaceuticals with improved biological properties compared with the parental products.

Novel Antifungal Polyene Amides from the Myxobacterium Cystobacter fuscus: Isolation, Antifungal Activity and Absolute Structure Determination

AbstractFor Abstract see ChemInform Abstract in Full Text.

Novel antifungal polyene amides from the myxobacterium Cystobacter fuscus: isolation, antifungal activity and absolute structure determination

Three new unstable metabolites, (6 E,10 Z)-2′- O-methylmyxalamide D ( 1 ), 2′- O-methylmyxalamide D ( 2 ) and (6 E)-2′- O-methylmyxalamide D ( 3 ) were isolated from the myxobacterium Cystobacter fuscus. The planar structures were elucidated by spectroscopic analyses to be geometrical isomers of a polyene amide related to a myxobacterial metabolite, myxalamide D ( 4 ). Their absolute stereochemistry was determined by synthesis of degradation products. Antifungal activities of 1– 3 as well as their acetates were evaluated against the phythopathogenic fungus Phythopthora capsici.

Structural studies and antifungal activity of unique polyene amides, clathrynamide A and three new derivatives, from a marine sponge, Psammoclemma sp.

Known polyene amide, clathrynamide A, and three novel related metabolites, debromoclathrynamide A, (4E,6E)-debromoclathrynamide A and (6E)-clathrynamide A, were isolated from an Okinawan marine sponge, Psammoclemma sp. The absolute stereochemistry of clathrynamide A was determined to be 3R,12R by the modified Mosher method. The structures of the three new compounds were elucidated by spectroscopic analyses as debromo derivatives and geometrical isomers. Their antifungal activities were also evaluated with a phytopathogenic fungus, indicating that both the bromine atom and double-bond geometry affected the activity.

ChemInform Abstract: Natural Products with Polyene Amide Structures

Abstract A general overview of the chemical structure, synthesis, natural sources and biological activity of different types of natural products with polyene amide structures is described. Isobutylamine, pyrrolidine and piperidine amides from Compositae, Piperaceae and Rutaceae families, which have a straight-chain fatty acid or the piperonal unit, mainly used as insecticides, have been considered. Open chain polyenamides isolated from fungals such as trichostatin, aranorosin and the compound YH-47522 are especially active as antibiotics. The manumycin family antibiotics and other polyene amides derived from 2-amino-3-hydroxycyclopenten-2-one, produced mainly by Streptomyces species, show antifungal, enzyme inhibitory activity and antibacterial action. Polyenoyltetramic acids have been isolated mainly from microbial sources or from sponges and they are potent antibiotics with antiviral and antiulcerative properties. The natural antitumor agents bearing the pyrrolo[1,4]benzodiazepine ring system, such as anthramycin, porothramycin A and mazethramycin also have the dienamide moiety and are produced by Streptomyces species. The macrolactamic ansamycin antibiotics present an aliphatic bridge with a dienamide moiety linking two non-adjacent positions of an aromatic nucleus, either naphthalene or benzene. They present a significant range of antitumor, antifungal, herbicidal, angiostatic, antiviral and antiprotozoal activity, and constitute the largest family of polyene amide natural products.

Differentiation inducers of human promyelocytic leukemia cells HL-60. Phenylcarbamoylbenzoic acids and polyene amides.

New inducers of the differentiation of human promyelocytic leukemia cells HL-60 to mature granulocytes, 4-(3, 4-diisopropylphenylcarbamoyl)benzoic acid (2c) and 4-(5, 6, 7, 8-tetrahydro-5, 5, 8, 8-tetramethylnaphthyl-2-carbamoyl)benzoic acid (2d), have been found. Two polyene amides which are structural hybrids of retinoic acid and the amide compounds 1a and 2d also exhibited the biological activity, and this result suggested a structural link between retinoic acid and the active aromatic amides.