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Kazuya Hayashi Danji Fukushima Koya Mogi 《Bioscience, biotechnology, and biochemistry》2013,77(10):1171-1178
Some physicochemical properties and amino acid composition of alkaline proteinase from Aspergillus sojae were found to be as follows: The isoelectric point was at pH 5.1. The molecular weight was 25,500 using the Sheraga-Mandelkern’s formula, based upon the values of the sedimentation coefficient , the intrinsic viscosity ([η] = 0.027 dl/g), and the partial specific volume . The enzyme contains 16.8% of nitrogen and is composed of 250 residues of amino acid; Asp31 Glu19, Gly27, Ala32, Val18, Leu14, Ile14, Ser28, Thr18, , Met2, Pro6, Phe7, Tyr8, Trp2, His5, Lys14, Arg3, (amide-NH3)20. 相似文献
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Owing to their ability to break glycosidic bonds in recalcitrant crystalline polysaccharides such as cellulose, the catalysis effected by lytic polysaccharide monooxygenases (LPMOs) is of major interest. Kinetics of these reductant-dependent, monocopper enzymes is complicated by the insoluble nature of the cellulose substrate and parallel, enzyme-dependent, and enzyme-independent side reactions between the reductant and oxygen-containing cosubstrates. Here, we provide kinetic characterization of cellulose peroxygenase (oxidative cleavage of glycosidic bonds in cellulose) and reductant peroxidase (oxidation of the reductant) activities of the LPMO TrAA9A of the cellulose-degrading model fungus Trichoderma reesei. The catalytic efficiency of the cellulose peroxygenase reaction (kcat = 8.5 s−1, and ) was an order of magnitude higher than that of the reductant (ascorbic acid) peroxidase reaction. The turnover of H2O2 in the ascorbic acid peroxidase reaction followed the ping-pong mechanism and led to irreversible inactivation of the enzyme with a probability of 0.0072. Using theoretical analysis, we suggest a relationship between the half-life of LPMO, the values of kinetic parameters, and the concentrations of the reactants. 相似文献
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Andrew Wojcicki 《Inorganica chimica acta》1985,100(1):125-133
Studies are reported on the chemical reduction of the homobinuclear bis(μ-phosphido) metal complexes (R = Ph or Me), and (M = Mo or W). Two reduction pathways have been observed which result in different two-electron transformations: (1) with Na or LiAlH4, electron transfer to yield the corresponding symmetric dianions of the type LnM(μ-PR2)2MLn2? without metalmetal bond and (2) with M′BR′3H(M′ = Li, Na, or K; R′ = Et or sec-Bu), hydride transfer to give monoanionic complexes of the type or (M = Fe, Mo, or W; L = CO or NO; R = Ph or Me). The monoanionic complexes can be deprotonated with n-BuLi at ?78 °C to the corresponding unsymmetric dianions (M = Fe; L = CO or NO; R = Ph) or symmetric dianions LnM(μ-PR2)2MLn2? (M = Mo or W; L = CO; R = Ph). The unsymmetric dianions isomerize on slight warming to the symmetric dianions, which undergo protonation by CF3COOH to yield the aforementioned monoanions. Reactions of several members of these three classes of binuclear anions with CF3COOH, alkylating reagents, 1,1-diiodohydrocarbons and metal diiodo complexes have resulted in the synthesis of new binuclear and trinuclear compounds. Examples include , (R = Me, Et, n-Pr, or i-Pr), (M = Mo or W; R = Me or Ph), , , , and Fe2Co(η5-C5H5)(CO)(NO)4(μ-PPh2)2. Synthetic and mechanistic studies on these reactions are presented. 相似文献
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Masako Matsuo Kiyoshi Sato Seizi Kitani Yukio Satomura 《Bioscience, biotechnology, and biochemistry》2013,77(3):353-356
A new sulfur-containing imidazole compound, m.p. 218~223°C (decomp.), in water), C11H19N3O3S was isolated from sclerotia of Sclerotinia libertiana and named sclerothionine. The chemical structure of sclerothionine was identified with 2-hydroxyethyl-ergothioneine which was synthesized from ethylene chlorhydrine and ergothioneine. 相似文献
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For a given graph G, ε(v) and deg(v) denote the eccentricity and the degree of the vertex v in G, respectively. The adjacent eccentric distance sum index of a graph G is defined as , where is the sum of all distances from the vertex v. In this paper we derive some bounds for the adjacent eccentric distance sum index in terms of some graph parameters, such as independence number, covering number, vertex connectivity, chromatic number, diameter and some other graph topological indices. 相似文献
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《Inorganica chimica acta》2006,359(4):1023-1030
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《Bio Systems》2009,95(3):233-241
A computer study of the prediction of the protein crystal’s shape and polymorphism of crystal’s structures within the limits resulting from the exploration of the Miyazawa–Jernigan matrix is presented. In this study, a coarse-graining procedure was applied to prepare a two-dimensional growth unit, where instead of full atom representation of the protein a two-type (hydrophobic–hydrophilic, HP) aminoacidal representation was used. The interaction energies between hydrophobic () aminoacids were chosen from the well-known HP-type models (), whereas interaction energies between hydrophobic and hydrophilic aminoacids () as well as interaction energies between hydrophilic aminoacids () were chosen from the range: , but not all values from this range fulfiled limitations resulting from the exploration of the Miyazawa–Jernigan matrix. Exploring every positively vetted combinations of energy interactions a polymorphism of the unit cell was observed what led to the fact that different final crystal’s shapes were obtained. 相似文献
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The objective of this work was to explore the hypothesis that nitric oxide (NO) affects Fe bioavailability in sorghum (Sorghum bicolor (L.) Moench) embryonic axes. NO content was assessed in embryonic axes isolated from seeds control or exposed to NO-donors, employing spin trapping electron paramagnetic resonance (EPR) methodology. NO donors such as sodium nitroprusside (SNP) and diethylenetriamine NONOate (DETA NONOate), released NO that permeated inside the axes increasing NO content. Under these conditions low temperature EPR was employed to study the labile iron pool. A 2.5 fold increase was observed in NO steady state concentration after 24 h of exposure to NO donors that was correlated to a 2 fold increase in the Fe labile pool, as compared to control axes. This observation provides experimental evidence for a potential role of NO in Fe homeostasis.Key words: iron, labile iron pool, nitric oxide, sorghumNitric oxide (NO) has a wide range of functions, among them promotion of growth and seed germination were described in several plant species.1 Evidences for its participation in Fe homeostasis in planta arise from the fact that Fe deficiency can be reverted enhancing NO level.2 Moreover, it is expected that NO acts as intercellular messenger3 being transported from the site of its synthesis. Nitrosylated Fe complexes, formed by reaction of NO with Fe2+ and biological thiols, have been proposed as NO carriers, since they are relative stable molecules.4The ability of Fe of changing its oxidation state and redox potential in response to changes in the nature of the ligand makes this metal essential for almost all living organisms.5 Fe-containing enzymes are the key components of many essential biological reactions. However, the same biochemical properties that make Fe beneficial might be a drawback in some particular conditions, when improperly shielded Fe can catalyze one-electron reductions of O2 species that lead to the production of reactive free radicals. The toxicity of Fe depends on the Fenton reaction, which produces the hydroxyl radical (·OH) or an oxoiron compound (LFeO2+) and on its reactions with lipid hydroperoxides.6Most of the current information about NO functions in plants comes from pharmacological studies using NO donors, which generate NO either spontaneously, or after metabolic activation. Moreover, NO production from numerous compounds strongly depends on pH, temperature, light and the presence of reductants.7 SNP and DETA NONOate have different kinetics and mechanisms of NO release. However, both are suitable compounds for long-term treatments, since their stability is higher than other NO donors.In this work we evaluated NO steady state concentration in sorghum embryonic axes 24 h after imbibition, in control seeds (distilled water) and in seeds placed either in 1 mM SNP or DETA NONOate. SNP contains Fe in its chemical structure, thus a control was carried out employing photodegraded SNP, which consist of 1 mM SNP solution which had been left under light until all NO was released from the molecule. As it is shown in FW (mg axis−1) Electrolyte leakage (%) NO (nmol g−1 FW) LIP(nmol g−1 FW) Control 6.8 ± 0.3 29 ± 2 2.4 ± 0.2 8 ± 1 SNP 10.8 ± 0.6* 20 ± 1* 6.0 ± 0.9* 19 ± 2* Photodegraded SNP 6.6 ± 0.3 27 ± 2 2.5 ± 0.6 9 ± 1 DETA NONOate 9.7 ± 0.9* 18 ± 1* 6.2 ± 0.6* 15.2 ± 0.5*