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 & Catalysis. The organization has 2143 authors who have published 3674 publications receiving 71071 citations. The organization is also known as: FFCLRP & FFCLRP-USP.

Modulation by ammonium ions of gill microsomal (Na+,K+)-ATPase in the swimming crab Callinectes danae: a possible mechanism for regulation of ammonia excretion

Abstract: The modulation by Na+, K+, NH4+ and ATP of the (Na+,K+)-ATPase in a microsomal fraction from Callinectes danae gills was analyzed. ATP was hydrolyzed at high-affinity binding sites at a maximal rate of V=35.4±2.1 U mg−1 and K0.5=54.0±3.6 nM, obeying cooperative kinetics (nH=3.6). At low-affinity sites, the enzyme hydrolyzed ATP obeying Michaelis–Menten kinetics with KM=55.0±3.0 μM and V=271.5±17.2 U mg−1. This is the first demonstration of a crustacean (Na+,K+)-ATPase with two ATP hydrolyzing sites. Stimulation by sodium (K0.5=5.80±0.30 mM), magnesium (K0.5=0.48±0.02 mM) and potassium ions (K0.5=1.61±0.06 mM) exhibited site–site interactions, while that by ammonium ions obeyed Michaelis–Menten kinetics (KM=4.61±0.27 mM). Ouabain (KI=147.2±7.2 μM) and orthovanadate (KI=11.2±0.6 μM) completely inhibited ATPase activity, indicating the absence of contaminating ATPase and/or neutral phosphatase activities. Ammonium and potassium ions synergistically stimulated the enzyme, increasing specific activities up to 90%, suggesting that these ions bind to different sites on the molecule. The presence of each ion modulates enzyme stimulation by the other. The modulation of (Na+,K+)-ATPase activity by ammonium ions, and the excretion of NH4+ in benthic crabs are discussed.

Pectinase production by Neurospora crassa: purification and biochemical characterization of extracellular polygalacturonase activity.

Abstract: The production of pectinase was studied in Neurospora crassa, using the hyperproducer mutant exo-1, which synthesized and secreted five to six times more enzyme than the wild-type. Polygalacturonase, pectin lyase and pectate lyase were induced by pectin, and this induction was glucose-repressible. Polygalacturonase was induced by galactose four times more efficiently than by pectin; in contrast the activity of lyases was not affected by galactose. The inducing effect of galactose on polygalacturonase was not glucose-repressible. Extracellular pectinases were separated by ion exchange chromatography. Pectate and pectin lyases eluted into three main fractions containing both activities; polygalacturonase eluted as a single, symmetrical peak, apparently free of other protein contaminants, and was purified 56-fold. The purified polygalacturonase was a monomeric glycoprotein (38% carbohydrate content) of apparent molecular mass 36.6-37.0 kDa (Sephadex G-100 and urea-SDS-PAGE, respectively). The enzyme hydrolysed predominantly polypectate. Pectin was also hydrolysed, but at 7% of the rate for polypectate. K m and Vmax for polypectate hydrolysis were 5.0 mg ml-1 and 357 µmol min-1 (mg protein)-1, respectively. Temperature and pH optima were 45°C and 6°0, respectively. The purified polygalacturonase reduced the viscosity of a sodium polypectate solution by 50%, with an increase of 7% in reducing sugar groups. The products of hydrolysis at initial reaction times consisted of oligogalacturonates without detectable monomer. Thus, the purified Neurospora crassa enzyme was classified as an endopolygalacturonase [poly(1,4-α-D-galacturonide) glycanohydrolase; EC 3.2.1.15].

Photoinduced NO release by visible light irradiation from pyrazine-bridged nitrosyl ruthenium complexes.

Abstract: The binuclear complex [RuII(NH3)5(pz)RuII(bpy)2(NO)](PF6)5 was prepared and characterized by elemental analysis, UV−vis, and IR spectroscopy. The complex UV−vis spectrum has presented bands at 242, 286, and 530 nm in acetate buffer solution at pH 4.5. The photochemical study by laser flash-photolysis at 532 nm showed the NO release account from the NO measured by a NO sensor. The quantum yield for NO release (0.025 ± 0.004 mol einsten-1) was determined with a laser flash-photolysis apparatus (Continuum Q-switched Nd:YAG laser). The major irradiation product of the [RuII(NH3)5(pz)RuII(bpy)2(NO)]5+ complex besides nitric oxide is [RuIII(NH3)5(pz)RuII(bpy)2(H2O)]5+.