重组过氧化氢酶与一种商品过氧化氢酶的性质比较

将重组过氧化氢酶和市售一种商品过氧化氢酶的性质进行了比较。重组酶的最适温度为70℃，某商品过氧化氢酶的最适温度为40℃；与这种商品过氧化氢酶相比，重组酶的热稳定性更好。重组过氧化氢酶和这种商品过氧化氢酶的最适pH都是7．0；重组酶和这种商品过氧化氢酶在pH3-8的范围内均较为稳定；重组酶在室温放置1个月后酶活力基本保持不变，而此种商品过氧化氢酶活力损失约70％；金属离子对重组酶和这种商品过氧化氢酶都有抑制作用，抑制程度有所不同；EDTA抑制这种商品过氧化氢酶的活性，但不抑制重组酶的活性。     

芦荟过氧化氢酶的分离纯化和性质研究

目的：获得库拉索芦荟过氧化氢酶纯品并对其性质进行研究。方法：采用硫酸铵分级沉淀,DEAESepharose阴离子交换层析,CM-Sepharose 阳离子交换层析和Sephacryl S-200 凝胶层析对酶蛋白进行分离纯化,采用SDS-PAGE 鉴定酶的纯度、分子质量。结果：从芦荟中分离纯化获得电泳纯的过氧化氢酶,纯化倍数为228.05倍,酶活力回收率为14.10%,比活力达17427.30U/mg。该酶的分子质量为239.90kD,亚基分子质量为60.60kD。推测该酶由4 个相同亚基构成。该酶最适温度为45℃,最适pH 值为7.5,以过氧化氢为底物测定该酶的表观Km 为34mmol/L。结论：成功分离纯化获得过氧化氢酶,该酶具有良好的热稳定性和酸碱耐受性。     

宠物咬胶用漂白牛皮中过氧化氢残留量测定及分解研究

目的探究不同温度、过氧化氢酶浓度、反应时间等对牛皮中过氧化氢分解速率的影响规律,以此指导生产中如何控制狗咬胶中过氧化氢残留量超标的问题。方法以生产宠物狗咬胶的漂白牛皮为原料,通过采用不同温度(30~70℃)的水和不同浓度(3%~5%)的过氧化氢酶溶液进行处理,对处理后的过氧化氢残留量进行测定。结果采用50℃温水浸泡漂白牛皮可以较快地去除其中残留的过氧化氢;或者采用浓度为3%的过氧化氢酶溶液,40~50℃,浸泡30 min左右可以更快地去除过氧化氢。根据处理条件的不同,通过试验拟合出方程可以比较准确地计算去除漂白牛皮样品中残留过氧化氢所需要的大体时间。结论通过热处理或者过氧化氢酶溶液处理,能够有效降低漂白牛皮中残留的过氧化氢含量,使最终产品符合要求。     

进出口脱皮花生涉税归类鉴定快速检测方法

建立脱皮花生涉税归类鉴定的快速检测方法——过氧化氢酶和过氧化物酶活性测定法。以pH 7.7的磷酸盐缓冲液提取花生中的过氧化氢酶,加入过氧化氢溶液后30℃水浴15 min,以0.1 mol/L高锰酸钾标准滴定溶液滴定剩余过氧化氢,通过高锰酸钾耗液量计算过氧化氢酶活动度;以pH 7.0的磷酸盐缓冲液提取花生中的过氧化物酶,25℃孵育30 min,加入愈创木酚和过氧化氢,在436 nm波长下,测定初始时和2 min后的吸光度值,计算两者之差ΔA,计算过氧化物酶活力。分别对鲜花生、出口生花生、干燥脱皮花生以及150℃烘烤30 min出口生花生和干燥脱皮花生进行过氧化氢酶和过氧化物酶活性测定。对数据做方差分析,结果有显著性差异。鲜花生中2种酶活性最高,经干燥后活性降低,150℃烘烤30 min后,2种酶失去活性。     

原料乳中过氧化氢酶定性检测方法的研究

为了监控原奶中是否掺有过氧化氢酶，采用人为添加过氧化氢到原奶中的方法，利用双氧水剂试纸条法测定，通过检测结果的判定，确定原奶中是否添加过氧化氢酶。结果表明，添加有过氧化氢酶的原奶，在用双氧水试纸条检测时为阴性，未添加过氧化氢酶的原奶，在用双氧水试纸条检测时为阳性。该方法用于实际原奶样、奶车样、奶仓样的检测，结果令人满意，检出限6mg／kg。     

罗丹明6G荧光猝灭法测定大米中过氧化氢酶活度

建立了荧光猝灭测定过氧化氢酶(CAT)活度的新方法，并完成测试条件优化。过氧化氢酶分解过氧化氢具有专一性，酶分解反应后剩余的过氧化氢与罗丹明6G发生荧光猝灭反应，Fe²⁺能够加速猝灭反应进程，荧光猝灭程度与酶活度有关联，根据酶分解反应前后荧光强度变化值(ΔF)确定过氧化氢酶活度(E)。结果表明，酶分解反应在15 min内完成，E在5×10^-5～3×10^-2 U/mL范围内与ΔF呈良好的线性关系：ΔF=2.64 2+6 155E,r=0.998 2,检测限为4.87×10^-6 U/mL。荧光猝灭法的各项指标均优于甲基红褪色光度法，在大米过氧化氢酶活度检测中得到应用。     

牡蛎和泥蚶过氧化氢酶的性质比较

对牡蛎和泥蚶过氧化氢酶(Cat)的性质进行比较。结果表明两者的PAGE谱带于同一位置，相对分了质量约为230kD，含有4个亚基。影响酶活力的温度相同，50℃以上酶活力明显下降；酶的最适pH5～8，但牡蛎Cat在酸碱条件下酶活力下降明显。     

甲基红褪色光度法测定大米中过氧化氢酶活性

探讨甲基红褪色光度法测定过氧化氢酶(CAT)活性新方法。酶促反应后剩余的过氧化氢与甲基红发生褪色反应,Fe3+能够加速反应进程,褪色程度与酶活性有函数关系。根据酶促反应前后吸光度变化值△A确定CAT活性E。结果表明,在20 min内,酶促反应符合一级动力学反应的特征,CAT活性E (U/mL)在0~0.12 U/mL范围内与△A呈良好的线性关系：△A = 0.001+2.276E (U/mL),r=0.9989,检测限为0.07 U/mL。该方法用于不同产地,不同年份大米过氧化氢酶活性测定,并与两种常用方法进行了对比,结果满意。。     

蜂花粉中过氧化氢酶活性测定新法的探讨

过氧化氢酶作为蜂花粉的新鲜度一项重要指标，是国家标准ＧＢ／Ｔ１１７５８－８９评定蜂花粉质量的重要依据之一。因此，建立一种准确、简单、快速的测定方法有十分重要意义，该论文主要论述利用经典仪器－Ｗａｒｂｕｒｙ呼吸计测定过氧化氢酶活性的实验方法，该方法具有较好的精确度、重现性，变异系数亦很理想。可以上升为蜂花粉中过氧化氢酶活性测定的法定方法。     

过氧化氢酶的功能及研究

过氧化氢酶是一类广泛存在于动物、植物和微生物体内的氧化酶,其功能是催化细胞内过氧化氢分解,防止氧化。在论述过氧化氢酶类型划分、结构特点及生理功能的基础上,对其分离纯化、活性测定、性质研究做了综述。     

板栗壳棕色素的抗氧化活性及其活性成分的分离、鉴定

板栗壳棕色素是一种重要的天然食用色素,本文研究了其光谱特性、抗氧化活性和化学成分组成,为板栗壳棕色素的深入应用提供依据。利用碱提酸沉等方法从板栗壳中提取出板栗壳棕色素,紫外和红外光谱法初步确定其光谱特性,并采用Folin-Ciocalteu法、苯酚-硫酸显色法和BCA法测定棕色素中总多酚、多糖和蛋白质的含量。以DPPH自由基清除法测定棕色素的抗氧化活性,采用色谱法分离纯化其中的化合物,并通过液相色谱、质谱与核磁对其进行鉴定。结果表明,板栗壳棕色素的水溶液在276 nm波长有最大吸收,红外光谱图显示出明显的多酚类物质特征。棕色素中总多酚、多糖和蛋白质含量分别为42.35%、13.75%和8.08%。棕色素对于DPPH自由基的IC₅₀为0.44 mg/mL,具有较强的抗氧化能力。从棕色素中分离得到10个多酚类化合物,分别为间苯二酚(1)、2-羟基-3',4'-二羟基苯乙酮(2)、邻苯二酚(3)、原儿茶醛(4)、没食子酸甲酯(5)、2,5-二羟基苯乙酮(6)、β-羟丙基香草酮(7)、原儿茶酸甲酯(8)、对香豆酸(9)和阿魏酸(10)。     

Potential Application of Hot Rehydration Alone or in Combination with Hydrogen Peroxide to Control Pectin Methylesterase Activity and Microbial Load in Cold-stored Intermediate-moisture Sun-dried Figs

ABSTRACT: Sun-dried figs contain a considerable amount of pectin methylesterase (PME) activity (22 JAM COOH/ min/g). The enzyme causes softening and loss of desired gummy texture in cold-stored intermediate-moisture (IM) sun-dried figs brought to a 28% to 29% moisture range. Partial reduction of PME activity (28%) delayed undesirable textural changes in IM figs rehydrated at 80 °C for 16 min. The heat treatment did not cause a considerable reduction in microbial load. However, the addition of 2.5% H2O2 to the rehydration medium at 80 °C reduced the initial total mesophilic aerobic count of figs by at least 90% and turned the figs from a brown color to a desirable and stable yellow-light brown. The in situ fig catalase remains after rehydration at 80 °C. Thus, by reducing the contact period of figs with H2O2 or by pureeing figs, it is possible to eliminate residual H2O2 and to obtain safe and SO2-free light-colored fig products.     

小麦和玉米中微生物污染和生长的快速检测

为了快速检测粮食及加工品中真菌、细菌等微生物的污染及生长的状况,选用了过氧化氢酶活性检测与经典的平板菌落计数检测进行比对试验。结果表明,对灰绿曲霉菌(Aspergillus glaucus)、黄曲霉菌(Aspergillus flavus)和枯草芽孢杆菌(Bacillus subtilits)等与粮食及加工品的储藏和流通品质及安全性密切相关的菌种进行梯度稀释菌悬液检测时,过氧化氢酶法检测值的相对偏差较小,且线性相关性系数均达到或大于0.99,其检测值与平板菌落计数法检测值的相关性系数均大于0.95。对于不同微生物污染程度的粮食及加工品,两种方法的检测数值变化趋势完全一致。相对于同一带菌量的样品,当粮食或加工品中的微生物处于生长状态时,过氧化氢酶检测法显示出更高的检测灵敏度,酶活性检测值超过微生物非生长态下同一带菌量样品检测值2倍以上。因此,过氧化氢酶检测法可以作为检测粮食及加工品中微生物污染及生长状况的有效手段。     

孔雀绿光度法测定蔬菜的抗氧化活性

研究用孔雀绿做显色剂分光光度法测定Fenton反应产生羟自由基的方法。产生的羟自由基与孔雀绿作用使溶液吸光度降低,利用吸光度的变化间接测定所产生的羟自由基。蔬菜的水提取液可清除溶液中的羟自由基,从而使孔雀绿溶液的褪色程度降低。测定了8种蔬菜的抗氧化活性,其中青椒的活性最强。     

COMPARISON OF METHODS TO VERIFY END POINT COOKING TEMPERATURE OF CHANNEL CATFISH (ICTALURUS PUNCTATUS) FILLETS

Cooking to 63C for 15 s remains an important step to ensure safe fish for human consumption. Methods for heat process verification have not been validated for channel catfish ( Ictalurus punctatus ). The present research compared extractable protein quantification, lactate dehydrogenase, acid phosphatase and catalase activity assays for verification of internal cooking temperature of channel catfish fillets. Ground raw catfish fillet samples (fresh and frozen) were cooked to 55, 60, 62, 63, 64 and 66C. Extractable protein, acid phosphatase and catalase activities decreased as internal cooking temperature increased, but lactate dehydrogenase activity remained unchanged. Samples cooked to 63C had extractable protein concentrations between 9.11 and 10.02 mg/g (95% confidence). Catalase was rapidly inactivated between 55 and 60C and may be suitable for identification of severely undercooked product. Acid phosphatase activity was influenced by method of storage (fresh versus frozen). A method based on total extractable protein appeared to be the most promising for determining the end point cooking temperature of catfish.

PRACTICAL APPLICATIONS

The most precise and reliable method to verify maximum cooking temperature attained during heat treatment of catfish fillets was total extractable protein. This finding may be useful for critical control point verification and may be valuable where claims of foodborne illness associated with catfish consumption are being litigated or investigated. To confirm gross undercooking, an easier test would be to measure catalase activity.     

Catalase Activity for Rapid Assessment of High Level Total Mesophilic Microbial Load in Milk

ABSTRACT: Total mesophilic microbial load (APC) is an important index for milk quality. It takes 48 h to enumerate APC with conventional plating methods. This report presents a rapid catalase activity test for monitoring APC in milk. Most aerobic microorganisms have strong catalase activities. Catalase activity in milk was monitored with a Pasteur pipette method in 5 min. The correlation between high APC numbers (> 4.0 log CFU/ml) and catalase activities was strongly correlated with r²=0.89. Classifying the APC into eight contamination groups was found to be a sound means of utilizing the resultant catalase activities to predict APC.     

Analysing the freshness of intact rice grains by colour determination of peroxidase activity

Freshness is an important palatability characteristic of rice grains. However, this characteristic deteriorates rapidly during dry storage. In the present study we have developed an indirect method to examine the freshness of rice grains harvested in different crop seasons or stored under conditions known to accelerate deterioration. Bulk samples of intact brown rice grains were soaked in dianisidine solution containing guaiacol and H₂O₂, and the optical absorbance of the incubation solution was determined colorimetrically. Alternatively, intact brown rice grains were incubated in a similar solution in the wells of a 96‐well microplate, with one grain per well, and the optical absorbance of the incubation solution was measured by a microplate reader. The results indicated that cultivar, storage duration and temperature significantly affected the activities of grain peroxidase. Marked differences in the development of purple colour in the incubation solutions and in vitro peroxidase activity were also found among the brown rice grains sampled in different seasons. The changes in colour of the incubation solutions measured by either of the above methods paralleled the changes in grain activity of peroxidase assayed using an in vitro method. The proposed method can differentiate brown rice grains harvested in different seasons. Moreover, this method, if combined with suitable statistical clustering procedures, can detect the blending status of fresh/old brown grains in a sample. The advantages of this test method using A₃₈₅ over the conventional enzyme activity assay are the rapidity and simplicity with which A₃₈₅ can estimate the in vitro determination of peroxidase activity of tested rice grains. Copyright © 2003 Society of Chemical Industry     

烟草与黄瓜花叶病毒互作中过氧化氢酶活性的变化

研究了12个不同抗性水平的烟草品种接种黄瓜花叶病毒前后过氧化氢酶活性的动态变化及其与烟草抗病性的关系。结果表明,接种病毒后抗、感品种的过氧化氢酶活性总体水平比对照降低,但酶活性的动态变化规律与烟草抗病性之间的相关性并不显著。利用DPS数据处理系统分析表明:酶活性变化差值及其平均值与病情指数之间均不存在显著相关性,说明以接种前后植物体内酶活性的变化值作为抗病性鉴定的指标在烟草-黄瓜花叶病毒体系中是不可行的。     

Effect of the iron biofortification on enzymes activities and antioxidant properties in germinated brown rice

This study evaluated the effects of germination and iron biofortification process on the enzymes activities and antioxidant properties of brown rice. The results showed that germination rates were increased after iron biofortification process. Accumulation of total iron in brown rice germinated in 2 g/L solution of ferrous sulfate was increased by 12.05–16.50 times compared with non-biofortified germinated brown rice. Furthermore, catalase and peroxidase activities were increased and decreased after this process, respectively. Total phenolic and flavonoid contents were significantly (p?<?0.05) increased 1.29 and 3.91 times compared with brown rice seed. The antioxidant activities were notably enhanced, especially at high iron concentrations. Hence, the iron biofortification process could be highly beneficial to improve the antioxidant capacities in brown rice. Total phenolic and flavonoid contents had a great correlation with DPPH and ABTS radical scavenging activities in cultivar Teyou 458 (r?=?0.9132–0.9439) but were not related to ferric reducing antioxidant power (FRAP) values. Moreover, in the same experiment, rice varieties had a great influence on the experimental results under the same iron biofortification conditions. This study concluded that cultivar Teyou 128 biofortified with 0.25 g/L ferrous sulfate solution during the germination process is appropriate to make functional food for human consumption.     

Variations of colour,polyphenol oxidase and peroxidase activities during the production of low temperature dried pasta in various durum wheat genotypes

This research was conducted to determine the effect of milling and pasta making on yellow pigment content, soluble brown pigment content, polyphenol oxidase (PPO) activity and peroxidase (POD) activity in semolina and pasta derived from ten durum genotypes. Results showed that pasta colour was impacted more by the milling than by pasta making. The loss of yellow pigment content, POD activity, PPO activity and soluble brown pigment content due to milling was 1.3×, 4.4×, 6.2× and 17.5×, respectively, greater than losses due to pasta making. Dry pasta contained 62%, 31%, 16% and 25% of the original yellow pigment content, brown pigment content and PPO activity and POD activity in the grain, respectively. Semolina yellow pigment content had a positive effect on pasta colour while semolina protein content, ash content and speck count had negative effects. These results indicate the importance of selecting genotypes that have high yellow pigment content and excellent milling qualities.