锰过氧化物酶(MnP)的研究进展

综述了国内外锰过氧化物酶（MnP)研究的最新动态。MnP是一种含有血红素的过氧化物酶,仅在白腐菌中发现。从产生MnP的微生物、MnP对Mn^2 的依赖性、催化机制、蛋白质研究进展、基因结构和基因表达的研究以及工业应用前景方面进行了系统概述。     

锰氧化细菌的生理生态功能与作用机制研究进展

锰的生物地球化学循环过程与全球尺度的营养元素循环紧密联系,是影响全球生态平衡及气候变化的重要因素之一。在自然界中,锰元素主要以氧化锰和含氧酸盐的矿物形式存在,近年来的研究观点普遍认为细菌介导的氧化作用是自然环境中锰氧化物形成的主要原因。锰氧化细菌广泛分布于海洋、锰矿土壤等生态系统,近期在植物微生态系统中也被发现,其生理生态功能未知。细菌的锰氧化过程是一个复杂的过程,多铜氧化酶和过氧化物(氢)酶是参与该过程的主要酶类,但关于其催化机制的认识尚不成熟。本综述系统探讨锰氧化细菌的种类和分布、细菌锰氧化作用的生理生态功能、参与细菌锰氧化作用的功能酶及其分子机制,总结这一研究领域所取得的成果和仍未解决的科学问题,并对今后的发展方向进行展望。     

植物谷胱甘肽过氧化物酶研究进展

氧化胁迫可诱导植物多种防御酶的产生,其中包括超氧化物歧化酶(SOD,EC1.15.L1)、抗坏血酸过氧化物酶(APX,EC1.11.1.11)、过氧化氢酶(CAT,E.C.1.11.1.6)和谷胱甘肽过氧化物酶(GPXs,EC1.11.1.9).它们在清除活性氧过程中起着不同的作用.GPXs是动物体内清除氧自由基的主要酶类,但它在植物中的功能报道甚少.最近几年研究表明,植物体内也存在类似于哺乳动物的GPXs家族,并对其功能研究已初见端倪.本文综述了有关GPXs的结构以及植物GPXs功能的研究进展.     

微生物除Mn(Ⅱ)机制及影响因素研究进展

锰是生物所必需的一种微量元素,但工业技术发展以及矿产资源的开发导致大量的Mn(Ⅱ)排放进入环境中对人体健康产生严重威胁.微生物修复技术可快速高效去除环境中的Mn(Ⅱ),且无二次污染,成为近年研究的热点.本文综述了除Mn(Ⅱ)微生物的种类与分布及其除Mn(Ⅱ)的机制,总结了影响微生物除Mn(Ⅱ)的因素,并展望了除锰微生物...     

植物抗坏血酸过氧化物酶研究进展(综述)

本文从酶的作用机制、酶学特征、分子生物学等方面综述植物抗坏血酸过氧化物酶（APX）的研究进展。     

植物谷胱甘肽过氧化物酶研究进展

氧化胁迫可诱导植物多种防御酶的产生, 其中包括超氧化物歧化酶(SOD, EC1.15.1.1)、抗坏血酸过氧化物酶(APX, EC1.11.1.11)、过氧化氢酶(CAT, E.C.1.11.1.6 )和谷胱甘肽过氧化物酶(GPXs,EC1.11.1.9)。它们在清除活性氧过程中起着不同的作用。GPXs是动物体内清除氧自由基的主要酶类,但它在植物中的功能报道甚少。最近几年研究表明, 植物体内也存在类似于哺乳动物的GPXs家族, 并对其功能研究已初见端倪。本文综述了有关GPXs的结构以及植物GPXs功能的研究进展。     

过氧化物酶体脂肪酸β氧化

除线粒体外,过氧化物酶体也是真核细胞脂肪酸β氧化分解的重要部位．过氧化物酶体β氧化过程包括氧化、加水、脱氢和硫解4步反应,主要参与极长链、支链脂肪酸等的分解．近年关于过氧化物酶体β氧化的研究活跃,在代谢途径及功能等方面有了新的认识,尤其在对相关代谢酶的研究中取得了较大进展．本文就过氧化物酶体β氧化相关进展作一综述．     

感染束顶病后香蕉过氧化物酶和多酚氧化酶活性变化(简报)

香蕉束顶病株的过氧化物酶（POD）和多酚氧化酶（PPO）的活性变化均呈单峰曲线，两者在香蕉束顶病毒（BBTV）浸染前期被诱导活性显著提高，接种后21和28d最高，42d后则都比健株低。侵染前期BBTV在体内的运转受抑，接种叶在接种后28d病毒含量最高，而顶叶则在35d后为最高。     

Mn(Ⅱ)氧化细菌Pseudomonas aeruginosa L3的分离、鉴定及氧化特性

【背景】Mn(Ⅱ)氧化细菌是一类可以沉积和氧化Mn(Ⅱ)从而形成固态锰氧化物的细菌,在生物地球化学和环境修复领域中引起了广泛关注,但目前所研究的Mn(Ⅱ)氧化模式菌株中大多来源海洋,土壤源Mn(Ⅱ)氧化细菌涉及较少。【目的】丰富土壤源Mn(Ⅱ)氧化细菌的来源与物种多样性,同时也为方铁锰矿型Mn₂O₃的潜在应用提供新菌种。【方法】从湖南省株洲市已关停的清水塘冶炼工业园区内筛选得到一株具有Mn(Ⅱ)氧化能力的铜绿假单胞菌(Pseudomonas aeruginosa) L3,并就其分离纯化、鉴定、生长曲线、pH变化、Mn(Ⅱ)氧化特性及锰氧化物制备等方面进行系统研究。【结果】Pseudomonas aeruginosa L3的菌液离心后的上清液及提取的绿脓菌素(pyocyanin, PYO)均具有Mn(Ⅱ)氧化能力,与菌液相比,上清液对Mn(Ⅱ)氧化的能力更强。进一步利用X射线衍射(X-ray diffraction, XRD)对Pseudomonas aeruginosa L3产生的锰氧化物进行晶相分析,发现该锰氧化物在2θ为32.951°和5...     

Screening, identification and kinetic characterization of a bacterium for Mn(II) uptake and oxidation

Following sample collection and screening at a number of Mn-associated mine sites in Northern Australia, a microbial strain was selected for its enhanced rate of Mn uptake. The strain was identified by phylogenetic analysis as a Rhizobium sp. Kinetic studies of Mn(II) uptake and oxidation by this strain in glucose-based media established that the uptake of Mn(II) was much greater than the conversion of Mn(II) to Mn oxide. Chemical analysis and scanning electron microscopy confirmed the production of significant amounts of polysaccharides by this strain. These polysaccharides may play a role both in enhancing Mn(II) accumulation and in minimizing Mn oxide production.     

Mn accumulation in a submerged plant Egeria densa (Hydrocharitaceae) is mediated by epiphytic bacteria

Many aquatic plants act as biosorbents, removing and recovering metals from the environment. To assess the biosorbent activity of Egeria densa, a submerged freshwater macrophyte, plants were collected monthly from a circular drainage area in Lake Biwa basin and the Mn concentrations of the plants were analysed. Mn concentrations in these plants were generally above those of terrestrial hyperaccumulators, and were markedly higher in spring and summer than in autumn. Mn concentrations were much lower in plants incubated in hydroponic medium at various pH levels with and without Mn supplementation than in field‐collected plants. The precipitation of Mn oxides on the leaves was determined by variable pressure scanning electron microscopy‐energy dispersive X‐ray analysis and Leucoberbelin blue staining. Several strains of epiphytic bacteria were isolated from the field‐collected E. densa plants, with many of these strains, including those of the genera Acidovorax, Comamonas, Pseudomonas and Rhizobium, found to have Mn‐oxidizing activity. High Mn concentrations in E. densa were mediated by the production of biogenic Mn oxide in biofilms on leaf surfaces. These findings provide new insights into plant epidermal bacterial flora that affect metal accumulation in plants and suggest that these aquatic plants may have use in Mn phytomining.     

Siro(haem)amide in Allochromatium vinosum and relevance of DsrL and DsrN, a homolog of cobyrinic acid a,c-diamide synthase, for sulphur oxidation

In the purple sulphur bacterium Allochromatium vinosum, the prosthetic group of dissimilatory sulphite reductase (DsrAB) was identified as siroamide, an amidated form of the classical sirohaem. The genes dsrAB are the first two of a large cluster of genes necessary for the oxidation of sulphur globules stored intracellularly during growth on sulphide and thiosulphate. DsrN is homologous to cobyrinic acid a,c diamide synthase and may therefore catalyze glutamine-dependent amidation of sirohaem. Indeed, an A. vinosumDeltadsrN in frame deletion mutant showed a significantly reduced sulphur oxidation rate that was fully restored upon complementation with dsrN in trans. Sulphite reductase was still present in the DeltadsrN mutant. DsrL is a homolog of the small subunits of bacterial glutamate synthases and was proposed to deliver glutamine for sirohaem amidation. However, recombinant DsrL does not exhibit glutamate synthase activity nor does the gene complement a glutamate synthase-deficient Escherichia coli strain. Deletion of dsrL showed that the encoded protein is absolutely essential for sulphur oxidation in A. vinosum.     

Multicopper oxidase involvement in both Mn(II) and Mn(III) oxidation during bacterial formation of MnO2

Global cycling of environmental manganese requires catalysis by bacteria and fungi for MnO₂ formation, since abiotic Mn(II) oxidation is slow under ambient conditions. Genetic evidence from several bacteria indicates that multicopper oxidases (MCOs) are required for MnO₂ formation. However, MCOs catalyze one-electron oxidations, whereas the conversion of Mn(II) to MnO₂ is a two-electron process. Trapping experiments with pyrophosphate (PP), a Mn(III) chelator, have demonstrated that Mn(III) is an intermediate in Mn(II) oxidation when mediated by exosporium from the Mn-oxidizing bacterium Bacillus SG-1. The reaction of Mn(II) depends on O₂ and is inhibited by azide, consistent with MCO catalysis. We show that the subsequent conversion of Mn(III) to MnO₂ also depends on O₂ and is inhibited by azide. Thus, both oxidation steps appear to be MCO-mediated, likely by the same enzyme, which is indicated by genetic evidence to be the MnxG gene product. We propose a model of how the manganese oxidase active site may be organized to couple successive electron transfers to the formation of polynuclear Mn(IV) complexes as precursors to MnO₂ formation.     

DNA cleavage by homo- and heterotetranuclear Cu(II) and Mn(II) complexes with tetrathioether-tetrathiol moiety

Novel homotetranuclear Cu(II) and heteronuclear Cu(II)-Mn(II) complexes with tetrathioether-tetrathiol moiety have been prepared and their DNA relaxation activities with plasmid pCYTEXP (5kb) were electrophoretically established. The cleavage products analyzed by neutral agarose gel electrophoresis indicated that the interaction of the metal complexes with supercoiled plasmid DNA yielded linear, nicked or degraded DNA. The relaxation activities of both homo- and heterotetranuclear (SK4) complexes are time- and concentration-dependent. The findings suggest that SK4 with potent nucleolytic activity is a good nuclease substitute in the presence of cooxidant. Furthermore, the observation of induction of DNA into smaller fragments by SK4 is also significant.     

In vitro studies indicate a quinone is involved in bacterial Mn(II) oxidation

Manganese(II)-oxidizing bacteria play an integral role in the cycling of Mn as well as other metals and organics. Prior work with Mn(II)-oxidizing bacteria suggested that Mn(II) oxidation involves a multicopper oxidase, but whether this enzyme directly catalyzes Mn(II) oxidation is unknown. For a clearer understanding of Mn(II) oxidation, we have undertaken biochemical studies in the model marine α-proteobacterium, Erythrobacter sp. strain SD21. The optimum pH for Mn(II)-oxidizing activity was 8.0 with a specific activity of 2.5 nmol × min⁻¹ × mg⁻¹ and a K _m = 204 μM. The activity was soluble suggesting a cytoplasmic or periplasmic protein. Mn(III) was an intermediate in the oxidation of Mn(II) and likely the primary product of enzymatic oxidation. The activity was stimulated by pyrroloquinoline quinone (PQQ), NAD⁺, and calcium but not by copper. In addition, PQQ rescued Pseudomonas putida MnB1 non Mn(II)-oxidizing mutants with insertions in the anthranilate synthase gene. The substrate and product of anthranilate synthase are intermediates in various quinone biosyntheses. Partially purified Mn(II) oxidase was enriched in quinones and had a UV/VIS absorption spectrum similar to a known quinone requiring enzyme but not to multicopper oxidases. These studies suggest that quinones may play an integral role in bacterial Mn(II) oxidation.     

Nitrogen fertilizers promote plant growth and assist in manganese (Mn) accumulation by Polygonum pubescens Blume cultured in Mn tailings soil

Abstract

This study examined how different nitrogen (N) forms and application levels promote plant growth and assist in manganese (Mn) remediation of Polygonum pubescens Blume (P. pubescens) cultured in soil with a high Mn level. The effects of ammonium chloride (a) and urea (u), at three application levels (10, 20, and 30?mg L^?1 N) and control (no N addition, CK) on the growth, Mn accumulation, and enzymatic anti-oxidative defenses of P. pubescens were examined. In general, both ammonium-N and urea-N promoted the plant mass and height of P. pubescens. The total Mn amount of roots, stems, and leaves in N treatments were higher (p?<?0.05) than that of CK. The ammonium-N treatments showed greater plant biomass and Mn accumulation compared to the urea-N ones. In general, the accumulations of Mn, Cr, Zn, and Cu were significantly lower (p?<?0.05) in the N fertilizer treatment than those in the control; while the accumulations of Pb were higher (p?<?0.05) in P. pubescens across all N fertilizer treatments than those in the control. The N addition decreased the contents of O₂^? and H₂O₂ in the leaves of P. pubescens, while increasing the activities of enzymatic anti-oxidative defenses.     

硫氧化细菌的种类及硫氧化途径的研究进展

硫,作为生物必需的大量营养元素之一,参与了细胞的能量代谢与蛋白质、维生素和抗生素等物质代谢。自然界中,硫以多种化学形态存在,包括单质硫、还原性硫化物、硫酸盐和含硫有机物。硫氧化是硫元素生物地球化学循环的重要组成部分,通常是指单质硫或还原性硫化物被微生物氧化的过程。硫氧化细菌种类繁多,其硫氧化相关基因、酶和途径也多种多样。近几年,相关方面的研究已取得很多进展,但在不同层面仍存在一些尚未解决的科学问题。本文主要围绕硫氧化细菌的种类及硫氧化途径的研究进展进行了综述。     

Determination of Mn(II) and Co(II) with Arsenazo III

Complex formation between Arsenazo III and Mn²⁺ and Co²⁺ at equilibrium has been investigated at pH 7.2, and the stoichiometry and stability of the complexes have been determined. The data indicate that Arsenazo III is suitable for determination of Mn²⁺ and Co²⁺ on the micromolar scale. The dissociation constants of the phosphate complexes of Mn²⁺ and Co²⁺ at pH 7.2 were estimated with Arsenazo III as 3.6 and 10 mM, respectively.     

Chromium(III) Oxidation Coupled with Microbially Mediated Mn(II) Oxidation

Abstract

Reductive immobilization of Cr(VI) has been widely explored as a cost-effective approach for Cr-contaminated site remediation. In soils containing manganese oxides, however, the immobilized form of chromium, i.e., Cr(III), could potentially be reoxidized. In this study, batch experiments were conducted to assess whether there were any microbial processes that could accelerate Cr(III) oxidation in aerobic, manganese-containing systems. The results showed that in the presence of at least one species of manganese oxidizers, Pseudomonas putida, Cr(III) oxidation took place at low concentrations of Cr(III). About 30–50% of added Cr(III) (10–200 μ M) was oxidized to Cr(VI) within five days in the systems with P. putida and biogenic Mn oxides. The rate of Cr(III) oxidation was approximately proportional to the initial concentration of Cr(III) up to 100 μ M, but the growth of P. putida was partially inhibited by Cr(III) at 200 μ M and totally stopped when it reached 500 μ M. Cr(III) oxidation was dependent upon the biogenic formation of Mn oxides, though the oxidation rate was not directly proportional to the amount of Mn oxides formed. Chromium(III) oxidation took place through a catalytic pathway, in which the microbes mediated Mn(II) oxidation to form Mn-oxides, and Cr(III) was subsequently oxidized by the biogenic Mn-oxides.