过氧化氢酶对固定化葡萄糖氧化酶稳定性的影响

本文通过重氮盐共价键合法把葡萄糖氧化酶接到交联琼脂糖上制备固定化酶。为了提高固定化酶的使用稳定性,把过氧化氢酶和葡萄糖氧化酶同时接到载体上,并研究了这两种酶在不同比例时对固定化葡萄糖氧化酶活力和稳定性的影响,随着加入过氧化氢酶量的增加,固定化葡萄糖氧化酶稳定性显著增加。所制得的固定化葡萄精氧化酶-过氧化氢酶在25℃下连续使用36h,活力几乎不变,失活半衰期可达1155h。     

融合表达过氧化氢酶提高多铜氧化酶稳定性及降解生物胺能力

多铜氧化酶(Multicopper oxidase,MCO)家族中的某些酶可以通过氧化反应降解食品中的胺类危害物生物胺.然而酶在催化时因为持续被氧化可能会影响整个反应过程中MCO的活性及稳定性,使酶的催化效率和降解生物胺的能力下降.文中成功在大肠杆菌Escherichia coli BL21(DE3)中构建并表达了来源...     

综合生物塘水体过氧化氢酶的活性,组成及其与过氧化氢的关系

在我国,关于水体酶学的研究尚未见诸报道。本文讨论了湖北黄州综合生物塘不同净化功能单元中过氧化氢酶(CAT)的组成(即未处理水样和通过孔径为3.0μ的滤膜的过滤水样各自所表现的活性)、CAT活性的变化趋势及其与底物(H_2O_2)浓度的关系。     

原位负染色法鉴定过氧化氢酶

原位负染色法鉴定过氧化氢酶曾庆平,郭勇（华南理工大学生物工程系,广州５１０６４１）关键词过氧化氢酶,色谱过氧化氢可使橙黄色的高铁还原为普蓝色的亚铁,而过氧化氢在过氧化氢酶作用下分解成水和氧后,便失去还原能力。因此,将过氧化氢酶原位固定于滤纸等支持介质...     

猪肝过氧化氢酶提取条件的研究

采用水浸提法提取猪肝过氧化氢酶。选择浸提时间、温度、料水比作为单因素进行梯度实验,确定其条件范围,再通过进一步的正交实验得到猪肝过氧化氢酶提取条件的优化组合,即料水质量比1：5,浸提温度25℃,浸提时间8h。     

文蛤过氧化氢酶的生物信息学分析

基于NCBI数据库,对文蛤过氧化氢酶基因(MmeCAT)进行生物信息学分析,旨在为文蛤过氧化氢酶的结构与功能的研究提供理论基础。结果表明,该基因编码511个氨基酸。文蛤过氧化氢酶分子量为58 181.29 Da,分子式为C_(2588)H_(3928)O_(767)N_(730)S_(20),理论等电点为8.05,属亲水蛋白。带负电荷氨基酸残基数(Asp+Glu)为63个,带正电荷氨基酸残基数(Arg+Lys)为65个。假设所有半胱氨酸全部形成胱氨酸,其消光系数为63 175 mol/L,相应的吸光度为1.086;假设所有的半胱氨酸均未形成胱氨酸时,消光系数为62 800 mol/L,相应的吸光度为1.079;其半衰期为30 h,脂肪族氨基酸指数为57.28,不稳定系数为27.77(40),可知文蛤过氧化氢酶为稳定蛋白质。亚细胞定位于过氧化物酶体,存在71个磷酸化位点和51个糖基化位点,无信号肽。二级结构以无规卷曲和α-螺旋为主,在物种进化上具有高度的保守性保守结构域预测表明,该基因编码蛋白可能属于典型单功能过氧化氢酶的第三分支。研究文蛤过氧化氢酶结构,能够为文蛤抗逆性品种选育提供理论基础。     

微生物过氧化氢酶的发酵生产及其在纺织工业的应用

微生物过氧化氢酶是一种重要的工业酶制剂,可以催化分解过氧化氢生成水和氧气。这一酶制剂在食品、纺织、医药等领域表现出广泛的应用潜力。生物工程和基因工程技术的进步推动了微生物过氧化氢酶的发酵生产。以下综述了微生物过氧化氢酶发酵生产的进展及其在纺织工业中的应用,同时讨论了微生物过氧化氢酶的发酵生产和纺织工业应用的未来趋势。     

细菌过氧化氢酶的分离、结晶及性质

过氧化氢酶又称触酶(Catalase EC 1.11.1.6),它广泛存在动植物和微生物的细胞内,是一种很有用的工具酶。细菌触酶目前国内外均无产品。本文就细菌酶的分离、结晶和鉴定及性质进行了研究。     

微胶囊固定化过氧化氢酶的制取及对H2O的分解作用

以乙基纤维素为膜材,用溶液干燥法制取了微胶囊固定化过氧化氢酶,探讨了制取过程中明胶的加入对微胶囊产率及固定化过化氢酶活性的影响,同时论述了存放时间、温度以及环境ＰＨ值对微胶囊固定化过氧化氢酶稳定性的影响,深入研究了微胶囊固定化过氧化氢酶对Ｈ２Ｏ的分解作用,获得了十分有意义的结果。     

Improvement in the long-term stability of freeze-dried mouse spermatozoa by adding of a chelating agent

This study demonstrates that a small amount of chelating agent in the freeze-drying solution is necessary to prevent the deterioration of spermatozoa during freeze-drying and subsequent preservation at 4 degrees C. We freeze-dried mouse epididymal spermatozoa in the solutions containing Tris-HCl and ethylenediaminetetraacetic acid (EDTA) as a chelating agent. Spermatozoa stored for various times up to 1 year at 4 degrees C were injected intracytoplasmically into individual oocytes, and the normality of chromosomes in fertilized oocytes was analyzed. In addition, embryos derived from freeze-dried spermatozoa were transferred into recipients to determine their developmental ability. Chromosomes were maintained well when spermatozoa were freeze-dried in a solution containing 10 mM Tris-HCl and 1mM EDTA (73%), and 57% of embryos developed to term. Of embryos derived from spermatozoa stored for 1 year, 65% developed into live offspring. On the other hand, when spermatozoa were freeze-dried in a solution containing 10 mM Tris-HCl and 0 or 50 mM EDTA, spermatozoa that maintained karyotypically normal chromosomes were 64% or 22%, and only 16% or 3% of embryos were developed to term, respectively. This finding suggested that mouse spermatozoa can be freeze-dried in a simple solution containing the same composition as that used to preserve extracted DNA.     

Improvement of lipase production by addition of catalase during fermentation

A batch fermentation process for lipase production with the recombinant strain Staphylococcus carnosus (pLipMut2) was studied in a bubble column. The rates of growth and lipase production in this type of fermentor were compared with results from shakeflasks. It was seen that cultivation in the bubble column resulted in a prolonged lag time and a reduced lipase activity in comparison to flask cultures. However, by addition of catalase during the fermentation in the bubble column this different behaviour could be avoided.Correspondence to: E. Wenzig     

Immobilized catalase: deactivation and reactor stability

The quasi-steady behavior of a continuous flow reactor in which hydrogen peroxide is decomposed by immobilized catalase is investigated. Under certain conditions, reactors involving such substrate-inhibited, self-poisoning reactions are susceptible to suddne failure and the reactor moves catastrophically from high- to low-conversion quasi-steady states. This exchange-of-steady-states phenomenon is ex-amined in the light of experimental evidence for the enzyme catalase from bovine liver. (c) 1993 John Wiley & Sons, Inc.     

Improvement of fungal arabinofuranosidase thermal stability by reversible immobilization

A gene encoding α-l-arabinofuranosidase (abfA) from Aspergillus niveus was identified, cloned, and successfully expressed in Aspergillus nidulans. Based on amino acid sequence comparison, the 88.6 kDa enzyme could be assigned to the GH family 51. The characterization of the purified recombinant AbfA revealed that the enzyme was active at a limited pH range (pH 4.0–5.0) and an optimum temperature of 70 °C. The AbfA was able to hydrolyze arabinoxylan, xylan from birchwood, debranched arabinan, and 4-nitrophenyl arabinofuranoside. Synergistic reactions using both AbfA and endoxylanase were also assessed. The highest degree of synergy was obtained after the sequential treatment of the substrate with endoxylanase, followed by AbfA, which was observed to release noticeably more reducing sugars than that of either enzyme acting individually. The immobilization of AbfA was performed via ionic adsorption onto various supports: agarose activated by polyethyleneimine polymers, cyanogen bromide activated Sepharose, DEAE-Sepharose, and Sepharose-Q. The Sepharose-Q derivative remained fully active at pH 5 after 360 min at 60 °C, whereas the free AbfA was inactivated after 60 min. A synergistic effect of arabinoxylan hydrolysis by AbfA immobilized in Sepharose-Q and endoxylanase immobilized in glyoxyl agarose was also observed. The stabilization of arabinofuranosidases using immobilization tools is a novel and interesting topic.     

Effect of deglycosylation on the stability of Aspergillus niger catalase

A sensitive, quantitative assay has been developed which measures the extent of liposome fusion by monitoring fluorescence resonance energy transfer between two lipid analogs originally in separate membranes. This transfer of photon energy from donor to acceptor molecules occurs only if both probes are in the same membrane. Energy transfer is measured as quenching of the donor probe's fluorescence emission. The extent of fusion was estimated by comparing the quenching due to the fusion protocol with the maximum quenching from “mock-fused” vesicles. This assay was used to investigate the effects of calcium ion concentration, calcium ion permeability, and lipid composition on fusion competence. The calcium concentration threshold and extent of fusion was a function of lipid composition. At a given molar percentage of phosphatidylserine, increasing the phosphatidylcholine content raised the threshold. The extent of fusion decreased when the molar percentage of phosphatidylserine was decreased. The inclusion of either cholesterol or phosphatidylethanolamine facilitated fusion competence, but the latter was more effective. Increasing the calcium ion permeability by adding the ionophore X-537a moderately enhanced the extent of fusion in most cases, although it never appreciably affected the threshold. X-537a did not enhance fusion in the presence of unsaturated phosphatidylethanolamine. Liposomes containing unsaturated phosphatidylethanolamine had an optimum calcium ion concentration for fusion in the mid-range of the divalent cation concentrations. We conclude that it is possible for large, unilamellar vesicles with near physiological molar percentages of phosphatidylserine and phosphatidylethanolamine to undergo divalent cation-induced fusion at calcium ion concentrations in the millimolar range. This finding provides a useful model system for investigating mechanisms of such phenomena as exocytosis and cell-cell fusion.     

Improvement in the resting-cell bioconversion of penicillin G to deacetoxycephalosporin G by addition of catalase

AIMS: To improve the resting cell bioconversion of penicillin G to deacetoxycephalosporin G (DAOG) by elimination of an oxidizing intermediate which inactivates the enzyme during the reaction. METHODS AND RESULTS: Resting cells of Streptomyces clavuligerus strain NP1 were incubated with penicillin G, required co-factors and decane in the presence of catalase or superoxide dismutase, and production of DAOG was measured. Catalase stimulated the bioconversion but superoxide dismutase did not. CONCLUSIONS: Production of hydrogen peroxide during the ring expansion reaction is at least partially responsible for enzyme inactivation. SIGNIFICANCE AND IMPACT OF THE STUDY: Catalase addition improves the bioconversion and will contribute to the eventual replacement of the current multi-step, expensive and environmentally-unfriendly chemical ring expansion by a biological route.     

Improvement of activity and stability of chloroperoxidase by chemical modification

Background  

Enzymes show relative instability in solvents or at elevated temperature and lower activity in organic solvent than in water. These limit the industrial applications of enzymes.     

Improvement of chloroperoxidase stability by covalent immobilization on chitosan membranes

Chloroperoxidase (CPO) from Caldariomyces fumago was optimally covalently immobilized on chitosan membranes pretreated with 0.8 M glutaraldehyde at pH 3.5 to give 3.18 mg CPO g⁻¹ support. Using monochlorodimedone (MCD) as assay substrate, the immobilized-CPO retained 40% activity at 50°C after 40 min whereas free CPO retained only 0.02%. The residual activity for immobilized-CPO was 99 and 58% compared with 68 and 43% for free CPO in the presence of 1.5 M urea and 300 μM H₂O₂, respectively, after 20 h.     

Kinetic properties and storage stability of catalase immobilized on to florisil

The covalent immobilization of bovine liver catalase (CAT) on to florisil via glutaraldehyde was investigated. Optimum immobilization pH and temperature were determined as pH 6.0, 10 degrees C respectively, while the amount of initial CAT per g of carrier and immobilization time was determined as 5 mg g(-1) and 120 min, respectively. The Vmax values for free and immobilized CAT were found to be 1.7 x 10(5) and 2.0 x 10(4) micromol H2O2 min(-1) mg protein(-1), respectively, whereas KM values were 33.3 mM and 1722.0 mM respectively. Operational stability was determined by using a stirred batch-type column reactor. Immobilized CAT retained about 40% of its initial activity after 50 uses. It showed higher storage stability than free CAT at 4 degrees C and 25 degrees C. Its storage stability increased with increasing relative humidity (RH) from 0 to 20% of the medium. The highest storage stability was obtained in 20% RH, however, further increase in RH from 40 to 100% significantly decreased the storage stability.     

Improvement of hyaluronic acid enzymatic stability by the grafting of amino-acids

Injection of hyaluronic acid (HA)-based hydrogels has proven to provide many therapeutic benefits. To increase the stability of HA-based products against enzymatic digestion, we modified hyaluronic acid by grafting various amino acids on its carboxylic group and then evaluated the enzymatic stability of the various conjugates in presence of a hyaluronidase. Our results showed that all amino acid-modified HA polymers were more resistant to degradation compared to the native HA albeit with variation according to the amino acids. Amino acids with carboxylate groups such as aspartic acid or with hydroxyl functions (threonine, serine or tyrosine) conferred a particularly strong resistance to HA towards enzymatic digestion. The HA-amino acid products were then cross-linked with butanediol diglycidyl ether (BDDE). The swelling properties of the formed hydrogels appeared close to native HA whereas the increased resistance towards hyaluronidase digestion remained. These results suggest that amino acid-modified HA derivatives can become promising material for viscosupplementation or drug delivery.