额尔齐斯河野生丁(鐬)蛋白酶、淀粉酶活性的研究

目的:研究温度、pH、金属离子对新疆额尔齐斯河野生丁(鐬)消化道蛋白酶、淀粉酶活性的影响.方法:酶学和生化法.结果:丁(鐬)蛋白酶活性,后肠＞前肠＞中肠＞肝胰脏;淀粉酶活性,后肠＞中肠＞前肠＞肝胰脏.肠道、肝胰脏蛋白酶的最适温度分别为35℃、40℃,淀粉酶的最适温度均为40℃.消化道各部位蛋白酶、淀粉酶的体外最适pH为7.5.在试验的离子浓度范围,高浓度Ag 、Cu2 抑制酶活力;高浓度Fe3 、Mg2 、Ca2 促进酶活力;Pb 、Ba2 对消化道酶活力影响依浓度和部位而变.结论:消化酶最适温度均高于所处环境温度,最适pH值变化范围偏碱性;不同浓度金属离子对丁(鐬)消化道各部位蛋白酶、淀粉酶活力高低表现出不同的变化趋势.     

草鱼、鲤、鲢、鳙和尼罗罗非鱼肝胰脏和肠道蛋白酶活性的初步探讨

草鱼、鲤、鲢、鳙肝胰脏和肠蛋白酶的最适pH值分别为8.7、8.7、7.6、7.6和8.4、8.7、8.0、8.4。草鱼、鲤和尼罗罗非鱼的肝胰脏蛋白酶活性比肠的高;鲢和鳙的肝胰脏蛋白酶的活性却比肠的低;尼罗罗非鱼胃的蛋白酶活性明显高于肝胰脏和肠的。草鱼、鲤和尼罗罗非鱼的肝胰脏蛋白酶活性明显高于鲢和鳙的;5种鱼的肠蛋白酶活性,鲤最高,尼罗罗非鱼最低,草鱼、鲢、鳙和尼罗罗非鱼间蛋白酶活性无明显差异。草鱼、鲤、鲢和尼罗罗非鱼的肠蛋白酶活性由前向后递减,而鳙的则以中肠活性最高。     

温度和pH对白斑狗鱼消化酶活性的影响

目的:通过改变酶的反应温度和pH,离体分析白斑狗鱼体内淀粉酶、蛋白酶和脂肪酶活性变化.方法:分别采用Folin酚法、DNS法和氢氧化钠滴定法测定蛋白酶、淀粉酶和脂肪酶活性.结果:在白斑狗鱼肝胰脏、胃二部位,淀粉酶的最适温度均为30℃,肠道淀粉酶的最适温度为40℃;最适pH值分别为4.0、2.0、7.0.肝胰脏、胃二部位脂肪酶的最适温度均为40℃,肠道脂肪晦的最适温度为50℃;最适pH值分别为5.0,4.0、5.0.肝胰脏、胃、肠道蛋白酶的最适温度均为50℃;最适pH值分别3.0、3.0、9.0.结论:在各自最适温度下,脂肪酶、淀粉酶、蛋白酶比活力均为:肠道＞胃＞肝胰脏.     

温度和pH对洞庭鲇鱼消化酶活性的影响

采用酶学分析方法研究了温度和pH对洞庭鲇鱼蛋白酶、脂肪酶和淀粉酶活力的影响。结果表明,在设定的温度和pH范围内,鲇鱼各消化酶的活力均随着温度和pH的升高呈现先升后降的变化趋势。其中,胃蛋白酶的最适温度为40℃,肝胰脏、前肠、中肠和后肠蛋白酶的最适温度为45℃;脂肪酶的最适温度均为35℃;胃淀粉酶的最适温度为35℃,其他部位均为30℃。胃、肝胰脏、前肠、中肠和后肠蛋白酶的适宜pH分别为2.0、8.5、7.5、8.0和8.0;脂肪酶的适宜pH均为7.5;淀粉酶肝胰脏的适宜pH为7.5,其余部位均为7.0。鲇鱼各消化酶活力存在器官特异性。在最适温度下,蛋白酶活力顺序为前肠>肝胰脏>胃>中肠>后肠,脂肪酶的活力顺序均为肝胰脏>胃>前肠>中肠>后肠,淀粉酶的活力顺序为肝胰脏>前肠>中肠>后肠>胃,各部位之间差异显著(P<0.05)。     

温度对兰州鲇消化酶活性的影响

测定了兰州鲇(Silurus lanzhouensis)胃、肝胰脏、前肠、中肠、后肠在不同温度(15℃、20℃、25℃、30℃、37℃4、2℃、47℃)条件下的蛋白酶、淀粉酶和脂肪酶的活性。结果表明,随温度的升高,各种酶活性的变化均表现为先增高后下降直至不能检出。消化道各部位蛋白酶的最适温度均为42℃;淀粉酶的最适温度除胃和肝胰脏为37℃外,其他部位均为30℃;脂肪酶的最适温度除后肠为30℃外,其他部位均为25℃。消化酶的最适温度高于其生活水域的水温,反映出消化酶作为酶蛋白的耐热性。最适温度下,蛋白酶活性前肠≈中肠>后肠>肝胰脏≈胃;淀粉酶活性前肠>中肠>肝胰脏>胃>后肠;脂肪酶活性中肠>后肠>前肠≈肝胰脏>胃。研究结果还表明,前肠和中肠是兰州鲇消化蛋白的主要部位,中肠是其消化脂肪的主要部位,而前肠是其消化淀粉的主要部位。在消化酶表现出活性的温度范围内,蛋白酶活性明显高于淀粉酶活性。实验还表明脂肪酶具有活性的温度范围较蛋白酶和淀粉酶窄。     

草鱼摄食两种蛋白质饲料后消化酶活性变动比较

用鱼粉和黄豆饼粉为主要蛋白源的试验饲料饲养草鱼两周,测定摄食前、后肠组织和肝胰脏蛋白酶、淀粉酶活性的变化以及不同时间前、中、后肠组织蛋白酶活性。结果表明:随摄食后时间的推移,鱼粉组肠组织蛋白酶活性迅速增高,到10h 达最大值,黄豆饼组则在15h 以后。两组肠组织淀粉酶活性均在10h 达到最大值。肝胰脏蛋白酶活性均在摄食后立即下降,到5h 降到最低值,随后缓缓升高,淀粉酶活性变化较平缓。肝胰脏蛋白酶与肠组织蛋白酶活性之间存在一种消长关系。总的看来,鱼粉组的蛋白酶、淀粉酶活性均高于黄豆饼组。前肠组织蛋白酶活性最高,中肠次之,后肠最低。     

固氮鱼腥藻的蛋白水解酶及其部分性质的研究

应用溶菌酶处理,超声破碎细胞,通过差异离心和解离剂处理,将细胞的不同部分分开。以水解α-酪蛋白反应检测蛋白水解酶活性,结果表明,在细胞的可溶部分、内细胞质膜、外膜及胞浆周围区均存在蛋白水解酶活性。异形胞可溶部分的蛋白酶活比营养细胞可溶的蛋白酶活高4—5倍。在固氮条件下,营养细胞可溶性蛋白酶反应最适温度为50—55℃,65℃时,酶活迅速下降。有Ca^2 5mmol／l时,蛋白酶在60℃稳定,无Ca^2 存在下,酶液在60℃预处理10分钟,酶活性丧失80％以上。酶反应的最适pH为8—10。而且氮饥饿之后,培养基的pH值对细胞蛋白酶活水平有明显影响,氮饥饿24小时内,蛋白酶活迅速增加,但在碱性条件下,酶活水平比在中性条件下要高得多。邻菲哕啉对蛋白酶活性有严重的抑制,EDTA仅有轻微抑制,而PMSF对细胞蛋白酶活的抑制作用,与细胞氮饥饿时间有关。     

嗜碱性短小芽孢杆菌碱性蛋白酶的研究III．酶的性质及应用

本文对嗜碱性短小芽孢杆菌(Alkaliphilic Bacillus pumilus)B45菌株产生的碱性蛋白酶性质进行了研究。该酶对酪蛋白水解的最适pH为10．0—10．5,在PH7-l0之间稳定,最适反应温度为45℃,稳定性较好。最适底物浓度为1％。四硬酸钠、氯化钙对酶有激活作用,三聚磷酸钠及碳酸钠在常温下对酶话力无影响,而在40℃时对活力略有抑制,加入0．2g／LCaCl2可以保护酶的活性。B 45蛋白酶对血、奶污布的去污效果明显,其去污力比一般洗衣粉高10-13倍。     

嗜热芽孢杆菌XJT—9503高温中性蛋白酶的研究 Ⅱ.酶的提纯及酶学特性研究

嗜热芽孢杆菌XJT—9503菌的发酵液经硫酸铵和丙酮分级沉淀分离纯化得到聚丙烯酰胺凝胶电泳均一的高温中性蛋白酶制品。SDS—PAGE测得酶分子量为3000。当以酪蛋白为底物时,酶反应最适温度为65℃,最适pH为7．在PH6．5—9范围内稳定。在65℃、0、02MpH7．5的磷酸缓冲液中的半衰期为54min。金属离子铜、汞、铝强烈抑制酶活,钙离子,镁离子对酶活有促进作用。     

氧化鱼油对草鱼(Ctenopharyngodon idelluspond)肝胰脏、肠道胆固醇、胆汁酸合成代谢的影响

为了研究氧化鱼油对草鱼肝胰脏、肠道胆固醇、胆汁酸合成代谢的影响,本研究以豆油、鱼油、氧化鱼油作为饲料脂肪源,分别设计鱼油组(6F)、豆油组(6S)、2%氧化鱼油(2OF)、4%氧化鱼油(4OF)及6%氧化鱼油(6OF)5组等氮、等能半纯化饲料,在池塘网箱养殖平均体重为(74.8±1.2)g草鱼72 d。采用实时荧光定量PCR(q RT-PCR)的方法,测定了草鱼肝胰脏、肠道组织中四种胆固醇合成相关酶HMGCR、SREBP2、CETP、ABCA1和胆汁酸合成关键酶CYP7A1的基因表达活性,结合血清、肝胰脏和肠道TC、TBA含量分析了胆固醇、胆汁酸的合成强度的变化。结果显示:(1)添加氧化鱼油后,草鱼肝胰脏HMGCR基因表达活性显著上调(p0.05),ABCA1和CYP7A1基因表达活性显著下调(p0.05),肝胰脏TC、TBA含量显著增加(p0.05);(2)添加氧化鱼油后,草鱼肠道HMGCR基因表达活性显著上调(p0.05),CYP7A1基因表达活性显著下调(p0.05),肠道TC含量显著增加(p0.05),而TBA含量显著减少(p0.05);(3)添加鱼油或氧化鱼油后,饲料∑PUFA含量与肝胰脏ABCA1基因表达活性呈显著正相关关系(p0.05),饲料MDA含量与肠道ABCA1基因表达活性呈显著负相关关系(p0.05)。结果表明,随着饲料氧化鱼油添加量的增加,在饲料∑PUFA含量减少和鱼油氧化产物MDA含量增加的交互影响下,肝胰脏和肠道细胞胆固醇合成能力、向细胞内转运胆固醇的能力增强,向细胞外转运胆固醇的能力、以胆固醇为原料合成胆汁酸的能力减弱,致使肝胰脏、肠道、血清胆固醇含量增加、而血清、肠道胆汁酸含量减少。肝胰脏胆汁酸含量增加,显示肝胰脏有胆汁酸淤积的发展趋势。预示着鱼体生理代谢可能需要更多的胆固醇以满足生理代谢的需要,而鱼体胆汁酸可能出现供给不足。     

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.