RESUMEN
The bopXYZ genes from the gram-positive bacterium Rhodococcus sp. strain 19070 encode a broad-substrate-specific benzoate dioxygenase. Expression of the BopXY terminal oxygenase enabled Escherichia coli to convert benzoate or anthranilate (2-aminobenzoate) to a nonaromatic cis-diol or catechol, respectively. This expression system also rapidly transformed m-toluate (3-methylbenzoate) to an unidentified product. In contrast, 2-chlorobenzoate was not a good substrate. The BopXYZ dioxygenase was homologous to the chromosomally encoded benzoate dioxygenase (BenABC) and the plasmid-encoded toluate dioxygenase (XylXYZ) of gram-negative acinetobacters and pseudomonads. Pulsed-field gel electrophoresis failed to identify any plasmid in Rhodococcus sp. strain 19070. Catechol 1,2- and 2,3-dioxygenase activity indicated that strain 19070 possesses both meta- and ortho-cleavage degradative pathways, which are associated in pseudomonads with the xyl and ben genes, respectively. Open reading frames downstream of bopXYZ, designated bopL and bopK, resembled genes encoding cis-diol dehydrogenases and benzoate transporters, respectively. The bop genes were in the same order as the chromosomal ben genes of P. putida PRS2000. The deduced sequences of BopXY were 50 to 60% identical to the corresponding proteins of benzoate and toluate dioxygenases. The reductase components of these latter dioxygenases, BenC and XylZ, are 201 residues shorter than the deduced BopZ sequence. As predicted from the sequence, expression of BopZ in E. coli yielded an approximately 60-kDa protein whose presence corresponded to increased cytochrome c reductase activity. While the N-terminal region of BopZ was approximately 50% identical in sequence to the entire BenC or XylZ reductases, the C terminus was unlike other known protein sequences.
Asunto(s)
Benzoatos/metabolismo , Genes Bacterianos , Oxigenasas/genética , Rhodococcus/genética , Biodegradación Ambiental , Escherichia coli/genética , Escherichia coli/metabolismo , Datos de Secuencia Molecular , Familia de Multigenes , Oxigenasas/metabolismo , Filogenia , Proteínas Recombinantes/metabolismo , Rhodococcus/clasificación , Rhodococcus/enzimología , Homología de Secuencia de AminoácidoRESUMEN
The two-component anthranilate 1,2-dioxygenase of the bacterium Acinetobacter sp. strain ADP1 was expressed in Escherichia coli and purified to homogeneity. This enzyme converts anthranilate (2-aminobenzoate) to catechol with insertion of both atoms of O(2) and consumption of one NADH. The terminal oxygenase component formed an alpha(3)beta(3) hexamer of 54- and 19-kDa subunits. Biochemical analyses demonstrated one Rieske-type [2Fe-2S] center and one mononuclear nonheme iron center in each large oxygenase subunit. The reductase component, which transfers electrons from NADH to the oxygenase component, was found to contain approximately one flavin adenine dinucleotide and one ferredoxin-type [2Fe-2S] center per 39-kDa monomer. Activities of the combined components were measured as rates and quantities of NADH oxidation, substrate disappearance, product appearance, and O(2) consumption. Anthranilate conversion to catechol was stoichiometrically coupled to NADH oxidation and O(2) consumption. The substrate analog benzoate was converted to a nonaromatic benzoate 1,2-diol with similarly tight coupling. This latter activity is identical to that of the related benzoate 1, 2-dioxygenase. A variant anthranilate 1,2-dioxygenase, previously found to convey temperature sensitivity in vivo because of a methionine-to-lysine change in the large oxygenase subunit, was purified and characterized. The purified M43K variant, however, did not hydroxylate anthranilate or benzoate at either the permissive (23 degrees C) or nonpermissive (39 degrees C) growth temperatures. The wild-type anthranilate 1,2-dioxygenase did not efficiently hydroxylate methylated or halogenated benzoates, despite its sequence similarity to broad-substrate specific dioxygenases that do. Phylogenetic trees of the alpha and beta subunits of these terminal dioxygenases that act on natural and xenobiotic substrates indicated that the subunits of each terminal oxygenase evolved from a common ancestral two-subunit component.
Asunto(s)
Acinetobacter/enzimología , Evolución Molecular , Oxigenasas de Función Mixta/genética , Oxigenasas de Función Mixta/metabolismo , Acinetobacter/genética , Secuencia de Aminoácidos , Benzoatos/metabolismo , Catálisis , Espectroscopía de Resonancia por Spin del Electrón/métodos , Escherichia coli/enzimología , Escherichia coli/genética , Flavinas/análisis , Hierro/análisis , Oxigenasas de Función Mixta/química , Oxigenasas de Función Mixta/aislamiento & purificación , Datos de Secuencia Molecular , Filogenia , Plásmidos , Especificidad por Sustrato , Temperatura , ortoaminobenzoatos/metabolismoRESUMEN
Inhalation of albuterol aerosol, 200 micrograms, delivered from metered dose inhalers via Aerochamber, elicited a highly significant improvement in peak expiratory flow rate from 70% to 84% and 91% predicted normal 5 and 20 minutes after treatment, respectively, in 30 asthmatic children 3 to 6 years of age. No significant increase in peak expiratory flow rate followed inhalation of placebo by a similar group of 16 asthmatic children. Use of the Aerochamber permits effective delivery of medication from metered dose inhalers to children as young as 3 years of age.
Asunto(s)
Albuterol/administración & dosificación , Administración por Inhalación , Aerosoles , Asma/tratamiento farmacológico , Niño , Preescolar , Femenino , Frecuencia Cardíaca , Humanos , Masculino , Ápice del Flujo Espiratorio , Pulso Arterial , Capacidad Pulmonar TotalRESUMEN
Determination of the number of particles greater than 0.5, 1, 2, 5, and 10 microM in the air before, during, and after cleaning of carpeting disclosed larger numbers of airborne particles during cleaning with portable vacuum cleaners than with central vacuum cleaners, and more airborne particles during cleaning of shag carpeting than shorter pile carpeting.