豆乳凝固酶产生菌UV-10发酵条件及其酶学性质的研究

豆乳凝固酶产生菌Bacillussp .UV 1 0的最适产酶条件 :初始pH6 4,温度 2 6℃ ,培养时间 1 9h ,需要较大的通气量。酶的最适作用pH和温度分别为 5 8和 70℃。在最适条件下酶活力可达 1 84u/mL。pH6 0～ 7 0稳定性较好。 6 0℃下 1h残余酶活 6 0 %。Ca²⁺,Fe²⁺,Mg²⁺,Na⁺对其有较强的激活作用 ,而Zn²⁺,Al相似文献   

嗜热脂肪芽孢杆菌β-半乳糖苷酶的性质

利用硫酸铵分级沉淀、离子交换层析 (DEAE- 2 2 )、Sephadex G- 75凝胶过滤从嗜热脂肪芽孢杆菌胞内提纯得到 β-半乳糖苷酶。研究表明 ,该酶最适表观反应温度和最适 pH分别为 6 0℃和 6 .4。在 50℃该酶具有良好的热稳定性。碱金属和碱土金属盐对酶有激活作用 ,重金属 Zn²⁺、Fe³⁺、Cu²⁺抑制酶的活力。巯基保护剂能明显增强酶的活力 ,而巯基结合试剂强烈抑制酶的活性。该酶对 β-     

乳酸克鲁维酵母β－半乳糖苷酶的分离纯化及性质研究

乳酸克鲁维酵母(Kluyveromyces lactis)经高压破壁后的粗提液,其β-半乳糖苷酶(E．C．3．2．1．23)比活力为5．56u／mg。经硫酸铵沉淀,丙酮沉淀,PAPMA—Sepharose 4B柱层析后,乳糖酶比活力达370u／mg,纯化了66．2倍,SDS—PAGE鉴定为一条带,分子量85000Da。酶作用的最适pH在6．4—6．8之间,最适温度40℃,50℃保温15min酶活丧失90％。以邻硝基苯一β一半乳糖苷(ONPG)为底物的米氏常数为2．78mmoI／L。酶的正常水解产物半乳糖对酶活力有一定的抑制作用,核糖强烈抑制酶活力,Fe²⁺、Zn²⁺、Cu²⁺、Ag⁺、PCMB和NBS都能使酶活丧失。Mg²⁺、Mn²⁺和还原剂巯基乙醇的存在能提高酶活力。     

木霉GXC产β-葡聚糖酶条件和酶学性质

研究了木霉GXC产 β 葡聚糖酶的条件。结果表明 ,最适产酶碳源为麸皮 ,氮源为硫酸铵 ;产酶的最适条件为 :初始pH为 4 0～ 5 0 ,30℃培养 44h。粗酶液经硫酸铵沉淀、SephadexG 2 5、SephadexG 1 0 0和DEAE SephadexA 50柱层析得到纯β 葡聚糖酶 ,SDS PAGE凝胶电泳显示一条带 ,测得分子量为 35kD。该酶最适反应pH5 0 ,最适反应温度为 60℃ ,在 40℃以下、pH4 0～ 5 0酶活力相对稳定。 5 0mmol L以下的Ca²⁺、Zn²⁺和Fe²⁺,以及 1 0 0mmol L以下的Co²⁺对酶活力有激活作用 ;而Cu²⁺和Fe³⁺具有抑制作用。     

黄绿木霉原生质体诱变育种研究*

利用正交实验方法研究了影响黄绿木霉(Trichoderma aureoviride)原生质体形成的因素,并利用紫外线、硫酸二乙酯、氯化锂几种因素复合诱变原生质体筛选高产纤维素酶菌株。影响原生质体形成的因子顺序是酶系统>菌龄>酶解时间>酶解温度,原生质体形成的最佳条件是0.5%蜗牛酶+0.5%溶菌酶+1.0%纤维素酶,菌龄为18h,酶解时间为3.0h,酶解温度为32℃;在该条件下原生质体产量可达到4.25×10⁶个mL^-1。Ca^{2+相似文献}   

棒曲霉22产木聚糖酶的研究

从105株霉菌和酵母菌中筛选到一株木聚糖酶活力较高的棒曲霉(Aspergillua clavatus)菌株22。该菌株适宜的产酶培养基为(g/1):蔗渣半纤维素30,NH₄NO₃ 5,酵母膏5,麸皮10,吐温801和少量无机盐,初始pH5.5。最适的孢子接种量为4.9×10⁶个/ml。在上述培养基中28℃振荡培养72h.木聚糖酶活力可达335.9u/ml。酶反应的最适温度为50℃;最适pH为4.8,在pH 6-11酶活性稳定。     

球孢白僵菌液体培养条件下淀粉酶的产生及活性影响因子

球孢白僵菌(Beauveria bassiana)是一种经典的昆虫病原真菌。利用自蚜虫分离的菌株SG8702对该菌产淀粉酶的条件及理化特性进行了研究。从二次旋转组合设计的13种液体培养基中,筛选出适合该菌产淀粉酶的培养基配方,其成份为可溶性淀粉0.3%,葡萄糖、蛋白胨和酵母粉各0.5%。含10.6个分生孢子/mL的此培养液恒温(25±1)℃振荡(120r/min)培养3.5d,菌丝生物量为16.7mg/mL,产淀粉酶量达527.1u/mg菌丝的最大值;培养液初始pH4～6最有利淀粉酶的产生,产酶量为1315.8～1439.2u/mg菌丝。淀粉酶活性在40℃、pH 4.0条件下最高,在pH 3～8范围内20℃下处理20min或在pH4～6范围内37℃下处理1 h酶活较为稳定;40℃下处理20min酶活保持90%以上,50℃和60℃下处理相同时间则酶活分别丧失52%和91%。一定浓度的Ca²⁺有利于酶活提高,但Cu²⁺、Mn²⁺、Na+、Hg²⁺、Fe²⁺和Mg²⁺等常见金属离子则不同程度地抑制酶活。     

枯草芽孢杆菌SA-22 β-甘露聚糖酶的纯化及其特性

利用硫酸铵沉淀、羟基磷灰石柱层析、Sephadex G-75凝胶过滤和DEAE-52离子交换柱层析的方法,将枯草芽孢杆菌SA-22 β-甘露聚糖酶纯化了30.75倍,同时,该酶比活达到3478056 u/mg,收率达到23.43%。利用SDS-PAGE凝胶电泳和Sephadex G-75凝胶过滤的方法测得枯草芽孢杆菌SA-22 β-甘露聚糖酶的分子量分别为38 kD和34 kD。实验发现该酶的最适pH为6.5,在pH 5～10的范围内稳定;该酶最适温度为70℃,在50℃保温4h后其活力不变,在60℃保温4 h后剩余酶活为74.2%,70℃的酶活半衰期为3h。实验还发现Hg²⁺对酶活力有明显抑制作用。该酶对槐豆胶和魔芋胶的K_m和V_max值分别为11.30mg/mL, 4.76mg/mL和188.68(μmol·mL^-1·min^-1), 114.94(μmol·mL^-1·min^-1)。     

青霉NXP25纤维素酶的产生及性质

青霉（Penicillium sp.）NXP25在5％玉米穗轴粉,3％（麦夫）,0.35％氮源10号和0.3％氯化钙组成的液体培养基（起始pH 5.0）中,10％接种量,29℃,280r/min振荡培养72h。在50℃温度下测定,发酵液内切-1,4-β-葡聚糖酶,外切-1,4-β-葡聚糖酶,β-葡糖苷酶和滤纸酶活力分别为841u/mL,13u/mL,24u/mL和46u/mL。各类型酶最适作用条件分别为pH4.8和60℃、pH5.0和50℃、pH4.     

Ca2+参与水霉菌丝细胞壁修饰的证据

以细胞壁崩溃酶-Driselflse短时间处理水霉(Saprozegma ferax)菌丝,pH5．0时可使原生质从菌丝亚顶端喷出,pH6．0～8．0时则不导致该现象发生;适当浓度EGTA的存在,可提高pH5．0时酶解引起的原生质喷出频率、使pH6．0～8．0时生长菌丝的顶端原生质也喷出、并且喷出多发生在菌丝最顶端;外加CaCl₂．不抑制菌丝顶端原生质的喷出,排除了Ca²⁺抑制酶活性的可能。随后的跟踪观察显示,长时间以缺Ca²⁺培养介质培养菌丝,同样能够导致菌丝顶端原生质喷出。上述研究结果表明,培养介质中Ca²⁺和H⁺对菌丝完整性的维持起调节作用,细胞壁上的Ca²⁺可能参与了水霉菌丝细胞壁物理特性的修饰。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Enterovirus 71 3C proteolytically processes the histone H3 N-terminal tail during infection

Highlights
1. The N-terminal tail of histone H3 is specifically cleaved during EV71 infection.
2. Viral protease 3C is identified as a protease responsible for proteolytically processing the N-terminal H3 tail.
3. Our finding reveals a new epigenetic regulatory mechanism for Enterovirus 71 in virus-host interactions.     

Detection of EBV and HHV6 in the Brain Tissue of Patients with Rasmussen’s Encephalitis

Rasmussen’s encephalitis (RE) is a rare pediatric neurological disorder, and the exact etiology is not clear. Viral infection may be involved in the pathogenesis of RE, but conflicting results have reported. In this study, we evaluated the expression of both Epstein-Barr virus (EBV) and human herpes virus (HHV) 6 antigens in brain sections from 30 patients with RE and 16 control individuals by immunohistochemistry. In the RE group, EBV and HHV6 antigens were detected in 56.7% (17/30) and 50% (15/30) of individuals, respectively. In contrast, no detectable EBV and HHV6 antigen expression was found in brain tissues of the control group. The co-expression of EBV and HHV6 was detected in 20.0% (6/30) of individuals. In particular, a 4-year-old boy had a typical clinical course, including a medical history of viral encephalitis, intractable epilepsy, and hemispheric atrophy. The co-expression of EBV and HHV6 was detected in neurons and astrocytes in the brain tissue, accompanied by a high frequency of CD8⁺ T cells. Our results suggest that EBV and HHV6 infection and the activation of CD8⁺ T cells are involved in the pathogenesis of RE.