RESUMEN
Compounds designed to mimic the tryptophan synthase alpha subunit reactive intermediate were found to be potent inhibitors of the enzyme. These compounds are herbicidal and the herbicidal mode of action was demonstrated to be due to disruption of tryptophan biosynthesis.
Asunto(s)
Herbicidas/síntesis química , Triptófano/antagonistas & inhibidores , Inhibidores Enzimáticos/síntesis química , Inhibidores Enzimáticos/farmacología , Herbicidas/farmacología , Triptófano/biosíntesis , Triptófano Sintasa/antagonistas & inhibidoresRESUMEN
Toxic and nontoxic peptides were isolated from the cyanobacterium Microcystis aeruginosa PCC 7806 by a procedure including extraction of cells with water-saturated 1-butanol, chromatography of the extract on silica gel plates and high performance liquid chromatography (HPLC) on Partisil-5. The toxin was shown to be only a minor constituent, being negatively charged and thus separable by electrophoresis, within the HPLC-purified fraction. It contained erythro-beta-methyl-D-Asp, D-Glu, D-Ala, L-Leu, and L-Arg known to be part of the Microcystis peptide-toxin with Mr 994. The major part of the HPLC-purified fraction was assigned, however, to a nontoxic peptide with a Mr of 956. Partial hydrolysis studies of the nontoxic peptide(s) revealed amino acid sequences composed of D-Glu, N-methyl-Phe, and 3,4-dehydro-Pro, aside from the common L-amino acids. Cyclic linkage in the nontoxic peptide(s) appears likely.
Asunto(s)
Aminoácidos/análisis , Microcystis/análisis , Oligopéptidos/aislamiento & purificación , Toxinas Biológicas/aislamiento & purificación , Cromatografía de Gases , Cromatografía Líquida de Alta Presión , Cromatografía en Capa Delgada , Electroforesis en Gel Bidimensional , Electroforesis en Papel , Cromatografía de Gases y Espectrometría de Masas , Hidrólisis , Espectrometría de Masas , Oligopéptidos/análisis , Espectrofotometría Ultravioleta , Toxinas Biológicas/análisisRESUMEN
Toxin was obtained from the cyanobacterium Microcystis aeruginosa PCC7941 by extracting freeze-dried cells with water-saturated, acidified n-butanol, diethyl ether-water distribution, reversed-phase thin-layer chromatography and silica high-performance liquid chromatography (HPLC). Two toxic peptide fractions resulted from HPLC. One of these fractions was analyzed by UV and NMR spectroscopy, amino acid analysis and fast atom bombardment mass spectroscopy. The following amino acid analysis and fast atom bombardment mass spectroscopy. The following amino acids were identified: beta-methyl-Asp, Thr, Glu, Ala, Val, Leu, Phe, Arg, N-methyldehydro-Ala and 3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid. Yet the mass spectroscopic data showed that the fraction was still composed of several, most likely cyclic peptides that did not stain with ninhydrin.