Catalase and Peroxidase Activity of Cu2+ Complexes

The relation between the structure of Cu²⁺ complexes and their catalytic activity in the decomposition of H₂O₂ can be used as a “molecular probe”, since it allows the deduction of the number of coordinated ligand groups in a Cu²⁺ complex from its catalytic activity. Since only coordinated ligand groups are oxidized by H₂O₂, further information about the coordination sphere of the metal ion can be obtained from the oxidation of certain parts of a ligand, which can be followed spectrophotometrically. The Cu²⁺ complexes of amides, polyamino acids, nucleotides, RNA, and native and denatured DNA have been investigated in this way. Kinetic studies provide an insight into the mechanisms of catalase and peroxidase reactions.     

Development of a catalase based biosensor for alcohol determination in beer samples

An amperometric biosensor based on catalase enzyme for alcohol determination was developed. To construct the biosensor catalase was immobilized by using gelatin and glutaraldehyde on a Clark type dissolved oxygen (DO) probe covered with a teflon membrane which is sensitive for oxygen. The working principle of the biosensor depends on two reactions, which one is related to another, catalyzed by catalase enzyme. In the first reaction catalase catalyzes the degradation of hydrogen peroxide and oxygen is produced and also a steady-state DO concentration occurs in a few minutes. When ethanol added to the medium catalase catalyzes the degradation of both hydrogen peroxide and ethanol and this results in a new steady-state DO concentration. Difference for first and the last steady-state DO concentration occurred in the interval surface of DO probe membrane, which related to ethanol concentration, are detected by the biosensor. The biosensor response depends linearly on ethanol concentration between 0.05 and 1.0 mM with a detection limit of 0.05 mM and a response time of 3 min. In the optimization studies of the biosensor phosphate buffer (pH 7.0; 50 mM) and 35 °C were established as providing the optimum working conditions. In the characterization studies of the biosensor some parameters such as reproducibility, substrate specificity, operational and storage stability were carried out. Finally, by using the biosensor developed and enzimatic-spectrophotometric method alcohol concentration of some alcoholic drinks were determined and results were compared.     

Kinetic method for acetylsalicylic acid determination based on its inhibitory effect upon the catalytic decomposition of H<Subscript>2</Subscript>O<Subscript>2</Subscript>

The catalytic reaction of catalase was investigated, by means of a Clark oxygen sensor, in the presence of various concentrations of acetylsalicylic acid. Michaelis-Menten kinetic parameters were determined from Lineweaver-Burk plots, obtained in the absence and in the presence of the inhibitor. The inhibition pattern, suggested by the Lineweave-Burk plots, corresponds to a fully mixed inhibition mechanism. A kinetic method, based on the indicator reaction: , was developed for the quantitative determination of acetylsalicylic acid. Calibration graphs of the reciprocal value of first-order rate constant versus acetylsalicylic concentration covered the concentration range (2.99–19.98)×10^–4 mol/L, while the detection limit was 4.12×10^–4 mol/L acetylsalicylic acid with a standard deviation of 2.1×10^–5 mol/L.     

丝裂霉素C、阿霉素与过氧化氢酶的相互作用

用荧光光谱法研究了水溶液中抗癌药物丝裂霉素C、阿霉素与过氧化氢酶分子间的结合反应。结果表明：药物对过氧化氢酶的内源荧光有较强的猝灭作用，形成复合物所产生的静态猝灭是引起过氧化氢酶荧光猝灭的主要原因。进一步依据荧光猝灭结果确定了药物-酶复合物的形成常数。     

Novel Trinuclear MnII/MnII/MnII Complexes – Crystal Structures and Catalytic Properties

The trinuclear manganese(II) complexes [Mn₃(L¹)₂(μ‐OAc)₄]·2Et₂O {HL¹ = (1‐hydroxy‐4‐nitrobenzyl)((2‐pyridyl)methyl)((1‐methylimidazol‐2‐yl)methyl)amine} ( 1·2EtOH ), [Mn₃(L²)₂(μ‐OAc)₄] {HL² = ((1‐methylimidazol‐2‐yl)methyl)(1‐hydroxybenzyl)amine} ( 2 ) and [Mn₃(L³)₂(μ‐OAc)₆] {L³ = bis(1‐methylimidazol‐2‐yl)methanone} ( 3 ) were synthesized. The compounds were characterized by X‐ray crystallography, mass spectrometry, IR, UV‐vis spectroscopy, and elemental analysis. The manganese atoms in 1 and 2 are bridged by phenol moieties of the ligands and acetates. In 3 they are only bridged by acetates in a mono‐ and bi‐dentate way. The resulting Mn···Mn distances are 3.233(1) Å ( 1 ), 3.364(1) Å ( 2 ) and 3.643(7) Å ( 3 ). In the present compounds different limiting cases for the phenomenon of the carboxylate shift are realized. Besides symmetric mono‐ and bi‐dentate bridging an unusual intermediate is also observed. 1·2EtOH is the first example of a trinuclear model for the OEC that shows catalase activity. Furthermore it was characterized by temperature dependent magnetic susceptibility measurements and a total spin ground state of S_t = 5/2 was found. The results for 1 reveals antiferromagnetic coupling between the central and the terminal manganese ions, with J = ?1.2 cm^?1, g = 2.00 (fixed), χ_TIP = 150×10^?6 cm³mol^?1.     

锰过氧化氢酶及其模型物研究进展

综述了近年来有关锰过氧化氢酶（ＭｎＣａｔ）活性中心结构、催化反应机理和模型物的研究进展。     

过氧化氢酶同银(I)离子作用的研究

用FT－IR、Raman和UV／Vis光谱法考察了过氧化氢酶同银（I）离子的相互作用。结果表明，过氧化氢酶可与Ag（I）离子反应生成棕黄色的物种，其特征吸收带在酰胺带Ⅰ、Ⅱ、Ⅲ和υc-s区域，且反应性随温度的升高而加强，当反应温度固定时，则随反应时间的增加而加强。在碱性介质中比在酸性介质中反应更加强烈。对反应原始状态的分析表明，过氧化氢酶同银（I）离子的反应是一个自动催化过程。     

过氧化氢歧化酶模拟酶的合成及催化性质的研究——meso-四(4-磺基苯)卟啉-锰(MnTPPS_4)作为模拟酶的研究

锰和meso-四(4-磺基苯)卟啉的螯合物MnTPPS_4可以作为过氧化氢歧化酶的模拟酶催化H_2O_2分解。本文首次探索将该模拟酶应用于生物传感器方面的可行性。在25℃、pH8.0条件下,模拟酶电极对1.0×10~(-3)～7.0×10~(-3)mol/L浓度范围的H_2O_2的响应呈线性。相关系数为0.9964。该电极的重现性,回收率良好,具有一定的抗干扰能力。这为进一步将该模拟酶代替天然酶应用于生物传感器奠定基础。     

The structure of the active oxygen complex of catalase: Model calculations

Ab initio SCF calculations are hereafter reported for two stereoisomers of the complex Fe(N₄C₆H₁₀) (O) (NH₃), a model of the active oxygen complex of catalase, whose structure is not known. The structure with the oxo ligand in axial position (Fig. 2a) is more stable than the one with the oxygen atom inserted into an iron-nitrogen bond (Fig. 2b) by 33 kcal/mole. Factors that might reduce this difference are discussed.     

Effect of the Nature of Crosslinking Agent on the Catalase‐Like Activity of Polystyrene‐Bound Glycine–Metal Complexes

Abstract

Catalase‐like activity of metal complexes of various crosslinked polystyrene‐supported glycines were carried out and correlated with the nature of crosslinking agent in the polymer support. Polystyrenes with 2 mol% divinyl benzene (DVB), ethylene glycol dimethacrylate (EGDMA), and 1,6‐hexanediol diacrylate (HDODA) crosslinking were used as polymer supports. Glycine functions were incorporated to the chloromethylpolystyrenes by polymer analogues reactions and complexed with Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), and Zn(II) ions. The metal uptake varied in the order: Cu(II) > Cr(III) > Mn(II) > Co(II) > Fe(III) > Ni(II) > Zn(II), and extent of metal uptake by various crosslinked systems varied with the nature of crosslinking agent. The polymeric ligands and the metal complexes were characterized by various analytical techniques. The catalytic activities of these metal complexes were investigated towards the decomposition of hydrogen peroxide and was found to decrease in the order: Co(II) > Cu(II) > Ni(II) > Cr(III) > Fe(III) > Mn(II) > Zn(II). With increasing rigidity of the crosslinking agent the catalytic activity also decreased.