RESUMO
Microorganisms were screened for the ability to modify the squalene synthase inhibitor squalestatin 1. Biotransformation of 1 by two actinomycetes, S15106 and S15138, yielded three products hydroxylated on the 4,6-dimethyl-oct-2-enoyl side chain either at the 6 position (5) or 7 position (4 two diastereoisomers), and lacking the acetyl ester from the C-1 side chain. Many strains were found to hydrolyse the 4,6-dimethyl-oct-2-enoyl or acetyl esters to yield squalestatins 2 or 3. The 3-methyl ester (6) of 1 was obtained using Fusarium sp. F13945. This fungus also produced a farnesoic acid derivative, possibly in response to inhibition of its squalene synthase by 1. The biotransformation products of 1 all retained potent squalene synthase inhibitory activity.
Assuntos
Actinomycetales/metabolismo , Compostos Bicíclicos Heterocíclicos com Pontes , Compostos Bicíclicos com Pontes/metabolismo , Farnesil-Difosfato Farnesiltransferase/antagonistas & inibidores , Ácidos Tricarboxílicos/metabolismo , Biotransformação , Compostos Bicíclicos com Pontes/química , Fusarium/metabolismo , Hidroxilação , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Estrutura Molecular , Streptomyces/metabolismo , Ácidos Tricarboxílicos/químicaRESUMO
During the screening of fungi for inhibitors of squalene synthase, Phoma sp. C2932 was found to produce three structurally related novel inhibitors. These compounds, designated the squalestatins, exhibited potent activity against both mammalian (rat liver) and fungal (Candida albicans) squalene synthase. Furthermore, they also had broad spectrum in vitro antifungal activity.
Assuntos
Antifúngicos/farmacologia , Compostos Bicíclicos Heterocíclicos com Pontes , Compostos Bicíclicos com Pontes/farmacologia , Farnesil-Difosfato Farnesiltransferase/antagonistas & inibidores , Ácidos Tricarboxílicos/farmacologia , Animais , Antifúngicos/química , Antifúngicos/isolamento & purificação , Compostos Bicíclicos com Pontes/química , Compostos Bicíclicos com Pontes/isolamento & purificação , Fungos/efeitos dos fármacos , Testes de Sensibilidade Microbiana , Ratos , Ácidos Tricarboxílicos/química , Ácidos Tricarboxílicos/isolamento & purificaçãoRESUMO
The isolation and structure determination of 6 analogues of the fungal protein synthesis inhibitor GR135402, from Graphium putredinis, is described. The relative potencies of the compounds as protein synthesis inhibitors and as in vitro antifungal agents provide interesting insights into the structure-activity relationships in this series.
Assuntos
Antifúngicos/isolamento & purificação , Antifúngicos/química , Antifúngicos/farmacologia , Fermentação , Proteínas Fúngicas/biossíntese , Testes de Sensibilidade Microbiana , Compostos Policíclicos/farmacologia , Relação Estrutura-AtividadeRESUMO
A novel antifungal antibiotic GR135402 has been isolated from a fermentation broth of Graphium putredinis which inhibited protein synthesis in Candida albicans but not rabbit reticulocytes. The spectrum of activity included C. albicans and Cryptococcus neoformans but not some other Candida species or Aspergillus species. Therapeutic efficacy in a mouse model of systemic candidosis was attained following parenteral dosing.
Assuntos
Antifúngicos/química , Antifúngicos/isolamento & purificação , Fungos Mitospóricos/química , Compostos Policíclicos/química , Compostos Policíclicos/isolamento & purificação , Inibidores da Síntese de Proteínas/química , Inibidores da Síntese de Proteínas/isolamento & purificação , Animais , Antifúngicos/farmacologia , Aspergillus/efeitos dos fármacos , Candida albicans/efeitos dos fármacos , Fermentação , Camundongos , Testes de Sensibilidade Microbiana , Fungos Mitospóricos/classificação , Compostos Policíclicos/farmacologia , Inibidores da Síntese de Proteínas/farmacologiaRESUMO
N-acetyl-D-neuraminic acid (Neu5Ac) aldolase (EC 4.1.3.3) has bee reported for synthesis of Neu5Ac,1-5 but there are no reports of processes which do not have significant drawbacks for large-scale operation. Here, Neu5Ac aldolase from an overexpressing recombinant strain of Escherichia coli has been used to develop an immobilized enzyme process for production of Neu5Ac. The enzyme was immobilized onto Eupergit-C and could be reused many times in the reaction. Base-catalyzed epimerization of N-acetyl-D-glucosamine (GlcNAc) yielded GlcNAc/N-acetyl-D-mannosamine (ManNAc) mixtures (c 4:1) which could be used directly in the aldolase reaction; however, inhibition of the enzyme by GlcNAc limited the concentration of ManNAc which could be used in the reaction by this approach. This necessitated the addition of a large molar excess of pyruvate (five- to seven-fold) to drive the equilibrium over to Neu5Ac; nevertheless, a method has been developed to remove the excess pyruvate effectively by complexation with bisulfite, thus allowing Neu5Ac to be recovered by absorption onto an anion-exchange resin. In a second approach, a method has been developed to enrich GlcNAc/ManNAc mixtures for ManNAc. ManNAc can be used at high concentrations in the reaction, thus obviating the need to use a large molar excess of pyruvate. Neu5Ac can be isolated from such reaction mixtures by a simple crystallization. This work shows the importance of integrated process solutions for the effective scale-up of biotransformation reactions.
Assuntos
Enzimas Imobilizadas/metabolismo , Escherichia coli/genética , Ácido N-Acetilneuramínico/biossíntese , Oxo-Ácido-Liases/metabolismo , 1-Propanol/química , Acetilglucosamina/química , Acetilglucosamina/farmacologia , Sequência de Bases , Biotransformação , Cristalização , Primers do DNA/química , Escherichia coli/enzimologia , Hexosaminas/química , Hexosaminas/farmacologia , Ácido Pirúvico/química , Proteínas Recombinantes/metabolismo , Solventes/química , Fatores de TempoRESUMO
The value of the FIC index as a predictor of synergy has been investigated using the antibacterial agents alafosfalin and cephalexin combined together with themselves in fully blind experiments. Under the conditions used, even weak interaction (FIC index 0.5-0.99) proved to be statistically highly significant. The use of such fully controlled blind studies would greatly enhance the credibility of many of the claims of synergy published in the literature. The representation of results as average isobolograms is only of value with combinations which show moderate to strong interaction.