Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto

About: Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto is a based out in . It is known for research contribution in the topics: Population & Genus. The organization has 2143 authors who have published 3674 publications receiving 71071 citations. The organization is also known as: FFCLRP & FFCLRP-USP.

Glucose and xylose stimulation of a β-glucosidase from the thermophilic fungus Humicola insolens: A kinetic and biophysical study

Abstract: β-Glucosidases activated by glucose and xylose are uncommon yet intriguing enzymes that may enhance cellulose saccharification efficiency, and are of interest for application in bioethanol production processes. The molecular mechanisms of activation are completely unknown, and the aim of this study was the kinetic and biophysical characterization of the stimulation of a β-glucosidase from Humicola insolens by glucose and xylose. The effects of the monosaccharides were concentration dependent, where in a stimulatory range (0.1–50 mmol L−1), the activity increased up to 2-fold; in a stimulatory-inhibitory range (50–450 mmol L−1 glucose or 50–730 mmol L−1 xylose), the enzyme continued to be stimulated, but the activity was lower than maximal. Above 450 mmol L−1 glucose or 730 mmol L−1 xylose, increasing inhibition occurred. Dynamic light scattering confirmed that the enzyme is monomeric (54 kDa) and kinetic, intrinsic tryptophan fluorescence emission and far ultraviolet circular dichroism analyses indicated that the enzyme possesses a catalytic site (CS) and a modulator binding site (MS). Glucose or xylose binding to the MS induces conformational changes that stimulate the catalytic activity at the CS. Glucose and xylose may compete with the substrate for the CS while the substrate competes with the monosaccharides for binding to the MS. The stimulation of the enzymatic activity by glucose and xylose, which compete for the same sites on the enzyme molecule, is not synergistic. These data reveal allosteric interactions between the MS and the CS in H. insolens β-glucosidase that result in fine modulation of the catalytic activity by the monosaccharides. A kinetic model was developed that accurately described the experimental data for enzyme stimulation by glucose and/or xylose. Understanding the regulatory mechanisms of the enzyme activity, with the aid of kinetic models, may be useful for the application of the enzyme in cellulose hydrolysis processes.

Divergence in wing morphology among sibling species of the Drosophila buzzatii cluster

Abstract: The Drosophila buzzatii species cluster consists of the sibling species D. buzzatii, D. koepferae, D. serido, D. borborema, D. seriema, D. antonietae and D. gouveai, all of which breed exclusively in decaying cactus tissue and, except for D. buzzatii (a colonizing subcosmopolitan species), are endemic to South America. Using a morphometric approach and multivariate analysis of 17 wing parameters, we investigated the degree of divergence in wing morphology among the sibling species of this cluster. Significant differences were obtained among the species and discriminant analysis showed that wing morphology was sufficiently different to allow the correct classification of 98.6% of the 70 individuals analysed. The phenetic relationships among the species inferred from UPGMA cluster analysis based on squared Mahalanobis distances (D2) were generally compatible with previously published phylogenetic relationships. These results suggest that wing morphology within D. buzzatii cluster is of phylogenetic importance. Zusammenfassung Das Artencluster Drosophila buzzatii umfasst die nahe verwandten Arten D. buzzatii, D. koepferae, D. serido, D. borborema, D. seriema, D. antonietae und D. gouveai. All diese Arten pflanzen sich ausschliesslich auf verfaulendem Kaktusgewebe fort. Mit Ausnahme von D. buzzatii (einer kolonisierenden subkosmopolitischen Art) sind alle diese Arten endemisch fur Sudamerika. In einem morphometrischen Ansatz und mittels multivariater Analyse von 17 Flugelparametern untersuchten wir die Flugelmorphologie dieses Artenclusters im Hinblick auf Divergenzen. Die einzelnen Arten weichen signifikant voneinander ab, so dass es moglich war, 98,6% von 70 untersuchten Tieren mittels dieser Unterschiede in der Flugelmorphologie korrekt zu klassifizieren. Die phenetischen Beziehungen zwischen den Arten, die mittels UPGMA-Clusteranalyse basierend auf dem Quadrat der Mahalanobis-Distanzen (D2) ermittelt wurden, stimmten im allgemeinen mit den bereits publizierten phylogenetischen Beziehungen uberein. Die Ergebnisse lassen den Schluss zu, dass die Flugelmorphologie ein wichtiges phylogenetisches Merkmal fur das D. buzzatii Artencluster sind.

Sesquiterpene lactones from Lychnophora ericoides.

Abstract: Two new sesquiterpene lactones, (4S,6R,7S,8S,10R,11S,16R)-1-oxo-3(10),8(16)-diepoxy-16-methylprop-1Z-enyl-16-methoxygermacra-2-en-6(12)-olide (1) and (4S,6R,7S,8S,10R,11S)-1-oxo-3,10-epoxy-8-angeloyloxygermacra-2-en-6(12)-olide (2), were isolated from Lychnophora ericoides. Their structures, including absolute configuration, were established by spectroscopic methods, including single-crystal X-ray analysis. Monitoring the furanoheliangolide metabolism of L. ericoides revealed an increase in biosynthesis during the plant flowering period.

Purification and biochemical characterization of β-xylosidase from Humicola grisea var. thermoidea

Abstract: β-d-Xylosidase production was maximal for Humicola grisea var. thermoidea grown on xylan as the sole carbon source. The main β-d-xylosidase activity was localised in the periplasm. β-Xylosidase was purified from crude extracts by heat treatment, ammonium sulfate precipitation and chromatography on DEAE-cellulose and Sephadex G-100. The purified enzyme was a monomer of molecular mass estimated to be 43 kDa by SDS-PAGE and gel filtration. Optima of pH and temperature were 6.0 and 50 °C, respectively. The enzyme activity was stimulated by Ca2+, Fe2+, and Mg2+. The purified β-xylosidase did not exhibit xylanase, carboxymethylcelullase, galactosidase, glucosidase, fucosidase or arabinosidase activities. The purified β-xylosidase hydrolysed xylobiose and xylo-oligosaccharides of up to five monosaccharide units. The enzyme had a Km of 0.49 mM for p-nitrophenyl-β-d-xylopyranoside and was not inhibited by its product, xylose.