RESUMO
l-Isovaline biosynthesis by TqaLFM-ti from Tolypocladium inflatum was demonstrated in vitro. The biochemical analysis of the α-ketoglutarate-dependent oxygenase TqaL-ti revealed that it produces (2S,3S)-3-ethyl-3-methylaziridine-2-carboxylic acid from l-isoleucine, thus exhibiting a stereoselectivity different from those of the reported homologues. Remarkably, a single mutation on I295 in TqaL-ti completely exchanged its stereoselectivity to produce the C-3 stereoisomer. TqaFM-ti generates d-isovaline from (2S,3R)-aziridine-2-carboxylic acid, suggesting that the stereochemistry of the TqaL product defines that of isovaline.
Assuntos
Aziridinas , Ácidos Cetoglutáricos , Oxigenases , Valina/análise , EstereoisomerismoRESUMO
Hymeglusin, a previously known eukaryotic hydroxymethylglutaryl-CoA (HMG-CoA) synthase inhibitor, was identified as circumventing the ß-lactam drug resistance in methicillin-resistant Staphylococcus aureus (MRSA). We describe the concise total syntheses of a series of natural products, which enabled determination of the absolute configuration of fusarilactoneâ A and provided structure-activity relationship information. Based on previous reports, we speculated that the target protein of this circumventing effect may be MRSA bacterial HMG-CoA synthase (mvaS). We found that this enzyme was dose-dependently inhibited by hymeglusin. Furthermore, overexpression of the MRSA mvaS gene and site-directed mutagenesis studies suggested its binding site and the mechanism of action.
Assuntos
Antibacterianos , Ácidos Graxos , Staphylococcus aureus Resistente à Meticilina , Pironas , Humanos , Antibacterianos/síntese química , Antibacterianos/química , Antibacterianos/farmacologia , Resistência beta-Lactâmica/efeitos dos fármacos , Relação Dose-Resposta a Droga , Staphylococcus aureus Resistente à Meticilina/efeitos dos fármacos , Testes de Sensibilidade Microbiana , Estrutura Molecular , Pironas/síntese química , Pironas/química , Pironas/farmacologia , Relação Estrutura-Atividade , Ácidos Graxos/síntese química , Ácidos Graxos/química , Ácidos Graxos/farmacologiaRESUMO
Kozupeptins A and B, novel antimalarial lipopeptides, were isolated from the culture broths of Paracamarosporium sp. FKI-7019. They exhibited potent antimalarial activity against chloroquine-sensitive and -resistant Plasmodium falciparum strains in vitro. The structural elucidation was accomplished by a combination of spectroscopic analyses and chemical approaches including a total synthesis of kozupeptin A. Synthetic kozupeptin A demonstrated a therapeutic effect in vivo, and an intermediate exhibited much higher antimalarial activity than kozupeptin A.