Activities of calpastatin, μ-calpain and m-calpain are stable during frozen storage of meat

The stability of μ-calpain, m-calpain and calpastatin activity during frozen storage of pork was studied in two experiments. In experiment 1, pork longissimus muscle was stored at either -20 or -80°C, and the samples were assayed at 2-3 weeks interval for calpain activity and calpastatin activity using a m-calpain stock solution stored at 4°C. No effects on calpain activity at either temperature were observed for up to 123 days of storage. Calpastatin activity was stable the first few weeks of storage, where after it decreased up to 143 days of storage independently of meat storage temperature. At day 143, calpastatin activity was also assayed using a newly purified stock solution of m-calpain giving a calpastatin activity equal to the activity measured day 0 using the original m-calpain stock solution. The m-calpain stock solution was unstable during storage at 4°C and the activity decreased in a linear manner and was highly related to the observed decrease in calpastatin activity during storage. In experiment 2, meat was stored as in experiment 1 and was assayed at 2-3week intervals for calpastatin activity using a m-calpain stock solution stored at either 4 or -80°C. As in experiment 1, the measured activity of calpastatin decreased during storage using m-calpain stock solution stored at 4°C and this decrease was highly correlated to the decrease in the activity of the m-calpain stock solution. The activity of the m-calpain stock solution stored at -80°C was constant during storage period of 153 days and likewise was the calpastatin activity measured using this stock solution. The relation between measured calpastatin activity and storage time of m-calpain stock solution was tested by adding, to a calpastatin assay, up to 10μL of a partly inactivated m-calpain solution. A negative relationship was observed between added inactivated m-calpain and measured calpastatin activity which suggests that the inactive m-calpain molecules mask some of the binding sites on calpastatin and thereby prevent some of the active m-calpain molecules from binding to calpastatin. This would underestimate the measured calpastatin activity. In conclusion, the calpains as well as calpastatin are stable during frozen storage of meat, and the observed decreased in calpastatin activity is due to instability of the m-calpain stock solution used in the calpastatin assay.     

西洋梨货架期间抗氧化活性及品质分析

探明西洋梨果实货架期间抗氧化活性和品质指标的变化。以康佛伦斯和凯斯凯德为试材,研究了两种西洋梨在货架期间的总抗氧化能力、自由基清除能力、抗氧化物质含量、品质指标以及酶活性。结果表明,货架期间,康佛伦斯的抗氧化活性呈先下降后上升的趋势,而凯斯凯德与之相反,康佛伦斯的抗氧化活性始终高于凯斯凯德。西洋梨总酚含量的变化趋势与其抗氧化活性基本一致,VC含量呈显著下降趋势,且康佛伦斯的总酚和VC含量始终高于凯斯凯德。在货架第6d时,康佛伦斯的硬度、可溶性固形物和还原糖含量均高于凯斯凯德,但可滴定酸却低于凯斯凯德。货架期间,康佛伦斯保持了较低的PPO活性和较高的POD活性。综上所述,康佛伦斯的抗氧化活性、品质及酶活性等各指标均好于凯斯凯德。      

大围山森林土壤中高产纤维素酶菌株的筛选及鉴定

通过初筛（刚果红纤维素水解试验和滤纸条分解试验）和复筛（利用3,5-二硝基水杨酸法测定内切纤维素酶活,滤纸酶活和β-葡萄糖苷酶活）,从大围山原始森林土壤中筛选高产纤维素酶菌株,获得4株具有高产纤维素酶活性的菌株。其中一株真菌16-7分解纤维素能力最强且酶活稳定,其内切羧甲基纤维素酶活为265.76U/mL,滤纸酶活为86.44 U/mL,β-葡萄糖苷酶活为39.16 U/mL;对真菌16-7分别进行形态学观察、分子生物学鉴定,初步确认为小刺青霉（Penicilliumspinulosum）。     

Beta-glucosidase activity in a Saccharomyces cerevisiae wine strain

Beta-glucosidase activity contributes to aroma formation during the winemaking process. This study investigated whether beta-glucosidase activity was expressed by wild Saccharomyces cerevisiae strains and by a laboratory strain. beta-Glucosidase activity was assayed on several culture media and under various growth conditions. The highest activities were obtained in Yeast Extract Peptone medium, but activity was also detected using grape juice as the growth medium, although a 25% drop activity was observed when anaerobic conditions were employed. A number of parameters affecting beta-glucosidase activity were evaluated. Optimal conditions for activity were pH 4 and a temperature of 40-50 degrees C. The results showed beta-glucosidase activity to be present during the process of winemaking, although different from the optimal conditions.     

CHANGES IN ACTIVITY OF SORGHUM LIPASE DURING MALTING AND MASHING

Lipase activity was monitored during malting and mashing of sorghum grains. All three sorghum varieties contained detectable lipase activity in the ungerminated form. Lipase activity changed only slightly during steeping for 24 hours but increased several fold in the course of germination. Between 24% and 60% of the lipase activity of the green malt was retained after kilning at 48°C but no activity was detected in the wort after mashing at 65°C. About 68% of the lipase activity of 72 hours old malt was detected in the plumule, while 29% and 3% were detected in the endosperm and radicle, respectively. Optimum activity was observed at pH 7.0.     

酪蛋白凝固与乳纤维蛋白溶酶活性的关系

采用分光光度计和SDS-PAGE电泳的方法,以鲜乳为原料,分别对酸沉,酶凝和钙凝的酪蛋白胶粒中的纤溶酶活性进行测定,对酪蛋白凝固与乳纤维蛋白溶酶活性的关系进行研究。结果表明,酸沉酪蛋白纤溶酶活性及总纤溶酶活性最高,分别为212.00 U/mL和250.00 U/mL,酶凝次之,Ca2+凝酪蛋白纤溶酶活性最低。     

色氨酸残基在双功能酶CCBE中的作用

应用化学修饰剂NBS对从绿色木霉生产的纤维素酶中分离出的既具有壳聚糖酶活性又具有纤维素酶活性的单一组分(简称双功能酶CCBE)进行了修饰。结果表明,CCBE的壳聚酶活性中心需一分子色氨酸残基,CMCase活性中心需两分子色氨酸残基;底物保护作用及酶解动力学研究表明,CCBE的壳聚酶活性中心及CMCase活性中心的一分子的色氨酸残基位于底物结合部位,而CMCase活性中另一分子色氨酸残基位于催化结构中心。     

籽瓜皮多酚的体外抗氧化及抗紫外线辐射作用研究

利用超声波辅助提取籽瓜皮中的多酚类物质,采用总铁还原能力(FRAP)、清除1,1-二苯基-2-苦肼基自由基(DPPH·)的能力、清除羟自由基的方法测定籽瓜皮粗提物的抗氧化性,并利用大肠杆菌固体培养基培养法观察其抗紫外线辐射作用。以高效液相色谱法对多酚萃取物的主要成分进行测定。结果表明,籽瓜皮多酚粗提物具有一定的体外抗氧化能力及抗紫外线辐射能力。其清除羟自由基的能力稍弱于Vc,清除DPPH自由基能力与2,6-二叔丁基对甲酚(BHT)相当,但其铁还原能力远比BHT强。给与使大肠杆菌致死率达到90%以上的辐射强度,与生理盐水相比,籽瓜皮多酚粗提物能提高大肠杆菌存活率。籽瓜皮多酚的抗氧化性及抗紫外线辐射的作用与其浓度都呈现出一定的线性相关性。籽瓜皮多酚的主要成分为没食子酸。     

瑞香狼毒提取物对水稻螟虫的杀灭活性研究

本文研究了瑞香狼毒根部粗粉乙醇提取物对水稻害虫大螟和二化螟的毒杀活性,当浓度为2.0g/L、作用时间为72h,乙醇提取物对大螟致死率为92.4%,二化螟的死亡率为20.9%。同时还系统研究了瑞香狼毒根部粗粉其它极性溶剂提取物对大螟和二化螟的胃毒活性、杀卵活性和内吸活性,结果表明瑞香狼毒对水稻大螟和二化螟具有一定的杀灭作用。     

Activity Staining of Pacific Whiting (Merluccius products) Protease

An activity staining method using SDS-substrate gel was used to determine Pacific whiting proteolytic activity. The most active protease band was resolved at an apparent M, of 39,500 corresponding to the activity of cathepsin L. The activity was more pronounced for ocean-caught Pacific whiting than Puget Sound Pacific whiting or ocean-caught arrowtooth flounder. Gel electrophoresis activity staining of proteolytic enzymes in Pacific whiting was not as sensitive as the TCA-azocasein assay but provided information on the molecular properties of the enzyme and a semi-quantitative estimation of activity.     

葛根抗氧化活性有效部位的筛选研究

对葛根提取物及其萃取物进行活性成分含量测定及抗氧化活性和总还原能力的测定。以DPPH自由基清除能力、羟基自由基清除能力和总还原能力代表其抗氧化活性,比较葛根各提取物及萃取物的抗氧化活性。采用Origin软件中的多项拟合计算活性试验的IC50值和A0.7值,并采用Pearson相关性分析测定活性成分含量与抗氧化活性相关性。最终测得结果表明,葛根70%乙醇提取物中含量最高的是总黄酮,含量为326.1 mg/g,水提物中总多糖含量最高,为183.9 mg/g。葛根提取物及其萃取物抗氧化活性顺序为:乙酸乙酯相>正丁醇相>水相。葛根70%乙醇提取物的乙酸乙酯萃取物的抗氧化活性最优。     

Amylase Activity in Banana Fruit: Properties and Changes in Activity with Ripening

Following subcellular fractionation and centrifugation, the amylase activity was located in the cytosol fraction of banana fruit. Over 80% of the observed activity (15—20 units per mg of protein) was attributed to α-amylase. The activity of β-amylase was tenfold lower and starch phosphorylase activity was low (17 μg inorganic phosphorus released per mg protein per 24 hr.). The activity of amylase in crude preparations was stimulated 40% by calcium ions. The amylase preparation, which was very stable at 4°C, hydrolyzed soluble potato starch and banana starch at similar rates. Maximum activity was observed between pH 6—7. The energy of activation of hydrolysis was 9.74 Kcal/mole. Amylase was quite active up to 62°C but rapidly lost activity above this temperature. There was an approximate twofold increase in amylase during the initial phase of ripening.     

Effect of mastitis on proteolytic activity in bovine milk

Proteolytic activity of milk was studied before, during, and after experimental-induced mastitis. An inoculum of Streptococcus agalactiae was infused into one quarter of each udder of six cows to elicit an infection. Bacteriological cultures and SCC of milk were used to monitor infection status. Sodium dodecyl sulfate-PAGE was used to measure proteolytic activity of milk. Inhibitor 6-amino-n-hexanoic acid was used to determine the relative proportion of plasmin and nonplasmin proteolytic activity of milk. Somatic cell count, total milk proteolytic activity, and nonplasmin proteolytic activity were higher in infected quarters than in quarters preinfection. After elimination of infections, SCC and nonplasmin proteolytic activity decreased to preinfection amounts. Total proteolytic activity of milk decreased after infections were cured but remained significantly higher than preinfection activity. This postinfection proteolytic activity in milk may be due to an increase in milk plasmin activity. Our data suggest that detrimental effects of mastitis on milk quality can continue after infection has been eliminated and milk SCC have returned to low values.     

鲣鱼蛋白肽谱效关系研究

采用鲣鱼为原料,以蛋白质回收率为指标,酶解制备不同工艺条件的样品。通过测定其黄嘌呤氧化酶(XOD)抑制活性、ORAC值、分子质量分布图谱和总氨基酸含量,构建鲣鱼蛋白肽体外化学活性与其分子质量分布图谱、总氨基酸含量图谱之间的谱效关系。结合超高效液相-质谱联用(LC-MS/MS)方法研究其降尿酸肽和抗氧化肽的分布。研究表明,鲣鱼蛋白肽的XOD抑制活性与其ORAC值具有显著的相关性。由多肽分子质量<1ku所占含量的分布区段和脂肪族氨基酸的含量可初步预测鲣鱼蛋白肽的化学活性。质谱分析表明,纯化组分的质谱基峰图在不同时间段的信号强度与鲣鱼蛋白肽的降尿酸活性和抗氧化活性具有明显的相关性。     

普洱茶固态发酵过程中多酚氧化酶酶学活性研究

以云南临沧凤庆大叶种晒青毛茶为原料进行普洱茶固态发酵,并且在发酵过程中对多酚氧化酶的最适pH、最适温度、最佳反应底物以及多酚氧化酶活性、酶蛋白含量和比活力进行研究。结果表明:多酚氧化酶在pH5.5、55℃的条件具有最大酶活性,EGC为最佳反应底物。普洱茶固态发酵过程中多酚氧化酶酶活性与比活力均呈波浪式上升趋势,发酵末期多酚氧化酶活性较初期增强,而酶蛋白含量总体呈下降趋势,但变化比较平稳。      

辣椒素对茶油的抗氧化与清除超氧阴离子自由基活性研究

研究了辣椒素对高温强化处理的油茶籽油的抗氧化性能及对O-2·的清除能力.添加抗氧化剂的油茶籽油在（60±2）℃恒温下强化处理后,用碘量法来测定过氧化值（POV）评判抗氧化性能.通过改良邻苯三酚自氧化法测定辣椒素清除自由基能力.样品经10d的60℃加热处理后,未添加抗氧化剂的POV值达到32.16 mmol/kg,添加质量分数0.10％辣椒素的POV值为17.03 mmol/kg.在相同浓度下,辣椒素的对油茶籽油的抗氧化效果介于同BHT与VE之间.当辣椒素的物质的量浓度为0.006 0 mmol/mL时,对O-2·自由基的清除率达到80.75％,此时维生素E为81.12％而BHT为77.15％.辣椒素具有较强的清除O-2·自由基的能力.     

Impact of genotype and micronutrient applications on nitrate reductase activity of tea leaves

Tea flush shoots comprising three leaves and a bud were collected from various clones (cultivars) from different experimental fields and analysed for nitrate reductase (NR) activity. Most of the cultivars of Assam type had higher NR activity, followed by Cambod and China types. NR activity was maximum in the clone UPASI‐9. It was found that NR activity could be used as a biochemical tool to predict the yield potential of cultivars at the initial stage of selection for a breeding programme. The activity was higher in the youngest part of the tea plant. With the existing methodology it was not possible to measure the NR activity in stem portions of the tea plant. There was a strong positive correlation between NR activity and amino acid contents of tea shoots. Inclusion of molybdenum in the foliar applied micronutrient mixture was found helpful in triggering the NR activity in a few clones and seedlings. Copyright © 2004 Society of Chemical Industry     

具有ACE抑制活性乳酸菌菌株的筛选与鉴定

以ACE抑制活性和蛋白水解活性为检测指标,选择138株乳酸菌为出发菌株,筛选出具有强ACE抑制活性的乳酸菌菌株.结果表明,筛选出具有强ACE抑制活性的4株乳酸菌,其中3株菌为瑞士乳杆菌,1株菌为干酪乳杆菌.瑞士乳杆菌KLDS1.0485和干酪乳杆菌KLDS1.0486比例为1:1,制成的发酵乳ACE抑制活性可达到61.55%.因此,组合瑞士乳杆菌KLDS1.0485和干酪乳杆菌KLDS1.0486可作为制备乳源ACE抑制肽的优良菌株.     

Toxin production by strains of Aeromonas hydrophila grown in laboratory media and prawn purée

Toxin production by four strains of Aeromonas hydrophila grown at 30 and 37 degrees C in two laboratory media and prawn purée was studied. Three different cell lines were used to test for cytotoxic activity, haemolytic activity was tested against rabbit and guinea pig erythrocytes, proteolytic activity was assayed with azo-casein and enterotoxic activity using the suckling mouse assay. Results showed reduced cytotoxic and haemolytic activities in prawn purée compared with the two media, but in most cases increased proteolytic activity. No enterotoxic activity was observed in prawn purée although it was occasionally detectable in both laboratory media.     

脂肪氧化酶对啤酒抗氧化性能的影响及其特性研究

分析了目前国内广泛使用的麦芽中的脂肪氧化酶的活性,并研究了脂肪氧化酶对啤酒抗氧化性能的影响。同时对麦芽中的脂肪氧化酶的基本酶学性质进行了调查,跟踪了工业化生产规模的制麦和糖化过程中的脂肪氧化酶的活性。结果表明麦芽含有脂肪氧化酶,在通常的糖化工艺条件下,仍有催化活性,导致麦汁和啤酒TBA增加。麦芽脂肪氧化酶的最适pH为6.5,在20～40℃之间表现出较高的活性,温度高于50℃时,热稳定性迅速下降。大麦经发芽之后脂肪氧化酶大幅度增加,峰值为原大麦的5倍左右,但是经过焙焦之后,酶活又大幅度下降。在糖化过程中,当醪液的温度低于60℃时,醪液中能检测出脂肪氧化酶的活性,是脂肪氧化酶催化氧化脂肪酸的关键阶段。