Degradation of phenol and toxicity of phenolic compounds: a comparison of cold-tolerant<Emphasis Type="Italic"> Arthrobacter</Emphasis> sp. and mesophilic<Emphasis Type="Italic"> Pseudomonas putida</Emphasis>

Phenol degradation efficiency of cold-tolerant Arthrobacter sp. AG31 and mesophilic Pseudomonas putida DSM6414 was compared. The cold-tolerant strain was cultivated at 10°C, while the mesophile was grown at 25°C. Both strains degraded 200 mg and 400 mg phenol/l within 48–72 h of cultivation, but the cold-tolerant strain produced more biomass than the mesophile. Both strains oxidized catechol by the ortho type of ring fission. Catechol 1,2 dioxygenase (C1,2D) activity was found intra- and extracellularly in the absence and in the presence of phenol. In the presence of 200 mg phenol/l, C1,2D activity of the mesophile was about 1.5- to 2-fold higher than that of the cold-tolerant strain. However, an initial phenol concentration of 400 mg/l resulted in a comparable enzyme activity of the cold-tolerant and the mesophilic strain. The two strains differed significantly in their toxicity pattern towards 12 aromatic (mostly phenolic) compounds at different growth temperatures, which was determined via growth inhibition in the presence of nutrients and toxicants. For the cold-tolerant strain, toxicity was significantly lower at 10°C than at 25°C. The mesophile showed a significantly lower susceptibility to high hydrocarbon concentrations when grown at 25°C compared to 10°C.Communicated by K. Horikoshi     

Adenine recognition: a motif present in ATP-, CoA-, NAD-, NADP-, and FAD-dependent proteins.

Adenosine triphosphate (ATP) plays an essential role in energy transfer within the cell. In the form of NAD, adenine participates in multiple redox reactions. Phosphorylation and ATP-hydrolysis reactions have key roles in signal transduction and regulation of many proteins, especially enzymes. In each cell, proteins with many different functions use adenine and its derivatives as ligands; adenine, of course, is present in DNA and RNA. We show that an adenine binding motif, which differs according to the backbone chain direction of a loop that binds adenine (and in one variant by the participation of an aspartate side-chain), is common to many proteins; it was found from an analysis of all adenylate-containing protein structures from the Protein Data Bank. Indeed, 224 protein-ligand complexes (86 different proteins) from a total of 645 protein structure files bind ATP, CoA, NAD, NADP, FAD, or other adenine-containing ligands, and use the same structural elements to recognize adenine, regardless of whether the ligand is a coenzyme, cofactor, substrate, or an allosteric effector. The common adenine-binding motif shown in this study is simple to construct. It uses only (1) backbone polar interactions that are not dependent on the protein sequence or particular properties of amino acid side-chains, and (2) nonspecific hydrophobic interactions. This is probably why so many different proteins with different functions use this motif to bind an adenylate-containing ligand. The adenylate-binding motif reported is present in "ancient proteins" common to all living organisms, suggesting that adenine-containing ligands and the common motif for binding them were exploited very early in evolution. The geometry of adenine binding by this motif mimics almost exactly the geometry of adenine base-pairing seen in DNA and RNA.     

Potentiometric and spectrophotometric equilibrium study on Fe(III) and new catechol-bisphosphonate conjugates

The coordination properties of mixed catechol-bisphosphonates towards Fe(III) are presented. From the potentiometric and spectroscopic results it was possible to state that iron coordination takes place only on the bisphosphonate moiety at acidic pH, and involves both catechol and bisphosphonate groups on two different iron(III) ions at higher pH values. Steric constracts keep both groups from chelating the same metal ion. Quantum mechanical calculations confirm this statement and allow to determine the minimum length of the linker for a stable conformation of complexes in which the same iron(III) ion is coordinated by both catechol and bisphosphonate.     

The signaling pathway of NADPH oxidase and its role in glomerular diseases

Abstract

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox), a major source of reactive oxygen species, is a critical mediator of redox signaling. It is well-documented that oxidative stress is associated with the development of glomerular diseases (GN). Hence, the Nox was also thought to be involved in the pathogenesis of GN. However, the expression of Nox in various GN was not consistent, the mechanisms by which the activity of the Nox enzymes in regulating renal cells remains unclear. Signaling pathways might be very important in the pathogenesis of GN. We performed this review to provide a relatively complete signaling pathways flowchart for Nox to the investigators who were interested in the role of Nox in the pathogenesis of GN. Here, we reviewed the signal transduction pathway of Nox and its role in the pathogenesis of GN.     

Electron spray ionization mass study on dioxygenation process in the reaction of catecholatoiron(III) complexes with molecular oxygen

The oxygenation reactions of two catecholatoiron(III) complexes, [Fe(TPA)(3,5-di-tert-butylcatecholate)]BPh₄ (1) and [Fe(TPA)(4-chlorocatecholate)]BPh₄ (2) (TPA = tris(pyridin-2-ylmethyl)amine), with O₂ have been investigated by means of ESI-MS spectrometry to elucidate the detailed mechanisms of oxygen atom insertion from O₂ into the catecholate ligands promoted by iron(III) complexes. Both 1 and 2 gave products formed by incorporation of two oxygen atoms into the catecholate ligands; 2,4-di-tert-butylmuconolactone for 1 and cis-dienelactone for 2. ESI-MS spectra of the products formed by the reaction with ¹⁸O₂ revealed the following points: (1) Two oxygen atoms of 2,4-di-tert-butylmuconolactone are mostly derived from ¹⁸O₂. (2) cis-Dienelactone is obtained as a mixture of mono- and double-¹⁸O-labeled species with a ratio of 50:50. These results suggest that the second oxygen atom is incorporated into muconic anhydride through nucleophilic attack on the carbonyl groups of muconic anhydride by the ¹⁸O-oxo-group of the metal center, and that this process competes with dissociation of muconic anhydride from the metal center.     

Roles for heme–copper oxidases in extreme high-light and oxidative stress response in the cyanobacterium Synechococcus sp. PCC 7002

The ctaCIDIEI and ctaCIIDIIEII gene clusters that encode heme–copper cytochrome oxidases have been characterized in the marine cyanobacterium Synechococcus sp. PCC 7002 and the inactivation of ctaDI was shown to affect high-light adaptation. In this study, Synechococcus sp. PCC 7002 wild-type, ctaDI, ctaDII, and ctaDI–ctaDII double mutants were grown under extreme high-light and oxidative stress to further assess the roles of cytochrome oxidases in cyanobacteria. Cells of the ctaDI mutant strain barely grew under extreme high-light illumination of 4.5 mE m⁻² s⁻¹, suggesting that CtaDI is required for high-light acclimation in Synechococcus sp. PCC 7002. The ctaDI–ctaDII double mutant cells unexpectedly tolerated extreme high-light intensity, indicating that the disruption of ctaDII gene suppresses the high-light sensitivity phenotype of the ctaDI single mutant. The ctaDII mutant cells also exhibited higher tolerance to the oxidative stress compound, methyl viologen, in the growth media. The ctaDII mutant and the ctaDI–ctaDII double mutant cells had approximately twofold higher levels of superoxide dismutase (SOD) activity, indicating that the disruption of ctaDII gene increased the capacity to decompose active oxygen species. These results suggest that the CtaII cytochrome oxidase may be involved with the oxidative stress response, including the control of SOD expression.     

Polyamine catabolism is involved in response to salt stress in soybean hypocotyls

The possible relationship between polyamine catabolism mediated by copper-containing amine oxidase and the elongation of soybean hypocotyls from plants exposed to NaCl has been studied. Salt treatment reduced values of all hypocotyl growth parameters. In vitro, copper-containing amine oxidase activity was up to 77-fold higher than that of polyamine oxidase. This enzyme preferred cadaverine over putrescine and it was active even under the saline condition. On the other hand, saline stress increased spermine and cadaverine levels, and the in vivo copper-containing amine oxidase activity in the elongation zone of hypocotyls. The last effect was negatively modulated by the addition of the copper-containing amine oxidase inhibitor N,N'-diaminoguanidine. In turn, plants treated with the inhibitor showed a significant reduction of reactive oxygen species in the elongation zone, even in the saline situation. In addition, plants grown in cadaverine-amended culture medium showed increased hypocotyl length either in saline or control conditions and this effect was also abolished by N,N'-diaminoguanidine. Taken together, our results suggest that the activity of the copper-containing amine oxidase may be partially contributing to hypocotyl growth under saline stress, through the production of hydrogen peroxide by polyamine catabolism and reinforce the importance of polyamine catabolism and hydrogen peroxide production in the induction of salt tolerance in plants.     

高分子络合树酯固定化多酚氧化酶的研究

为探索新的固定化酶方法,以漆酚-酪氨酸树酯为固定化酶载体,与Cu²⁺络合制备成高分子络合剂,对多酚氧化酶固定化,实验结果表明,这种固定化方法是可行的.固定化多酚氧化酶的适宜pH值为6.64和7.17,在60℃放置25 min后活力保留50.7%,以邻苯二酚为底物的米氏常数为1.49×10^－2 mol/L,较游离酶略小.根据实验结果提出了固定化酶模型.