对硝基苯氨甲酰甲基溴对甘油醛-3-磷酸脱氢酶的抑制

甘油醛-3-磷酸:NAD氧还酶(甘油醛-3-磷酸脱氢酶,酶学委员会编号1.2.1.12)是一个典型需要巯基的酶。许多巯基试剂如碘代乙酸或对氯汞苯甲酸等皆能完全抑制酶的活力。近年来一些作者曾利用标记的碘代乙酸研究了酶和抑制剂的结合当量。我们发现对硝基苯氨甲酰甲基溴(以下简     

小麦老化叶片蛋白水解酶的某些生化特性的研究（简报）

小麦叶片蛋白水解酶最适pH为5．0左右;最适温度：扬麦五号品种为50℃,野生一粒为45℃。碘乙酸、苯甲基磺酰氟明显抑制蛋白水解酶活力,前者大于后者;而半胱氨酸明显激活其活性。对小麦老化叶片起主要作用的是巯基类蛋白水解酶,丝氨酸蛋白酶也起一定作用。     

长叶车前花叶病毒上海分离株外壳蛋白赖氨酸残基的修饰对感染及重组的影响

长叶车前花叶病毒上海分离株外壳蛋白中有二个赖氨酸残基。完整的病毒颗粒或外壳蛋白在pH8.5条件下,只有一个赖氨酸残基与三硝基苯磺酸反应。如果有4M尿素存在,则有两个赖氨酸残基和一个半胱氨酸巯基被修饰。三硝基苯磺酰化的HRV_(sh)病毒颗粒的感染力丧失90%以上。HRV_(sh)的外壳蛋白经三硝基苯磺酸修饰后不能与HRV_(sh)-RNA重建。这些结果清楚地表明两个赖氨酸残基中一个位于病毒颗粒表面,另一个则包在病毒颗粒中。表面那个赖氨酸残基为HRV_(sh)的感染所必需。     

水稻疏基蛋白酶抑制剂的分子修饰与其对稻瘟病菌的抑制作用

水稻巯基蛋白酶抑制剂经用二硫苏糖醇,对氯汞苯甲酸和碘乙酸修饰后,对木瓜蛋白酶的抑制活性并无改变;用Ｎ－乙基顺丁烯二酰亚胺与ＣＰＩ反应,可以测出ＣＰＩ分子内有１９个巯基被修饰,被修饰后,抑制活性仍无改变,表明水稻ＣＰＩ的抑制活性不需要巯基参与;应用Ｎ－溴代丁二酰亚胺与ＣＰＩ反应,可测出ＣＰＩ分子内有２个Ｔｒｐ被修饰,修饰后,抑制活性全部丧失,表明Ｔｒｐ是保持抑制活性所必需的基因,水稻巯基蛋白酶抑制剂     

竹红菌甲素引起红细胞膜蛋白的光敏交联

为了探讨竹红菌甲素对红细胞膜蛋白的光敏交联机理,我们使用了一些专一性及非专一性的基团修饰剂来修饰膜蛋白,试图说明膜蛋白的光敏交联究竟是由膜蛋白的巯基光氧化所引起的,还是膜蛋白的氨基酸与其侧链氨基之间的交联所引起的。我们分别采用N-乙基顺丁烯二酰抱亚胺(NEM)修饰膜蛋白的巯基,用N-溴代琥珀酰亚胺(NBS)来修饰色氨酸残基,用乙氧甲酸酐(DEP)修饰组氨酸残基,及用琥珀酸酐(SA)修饰氨基。测定了红细胞膜修饰前后及有竹红菌甲素存在时,光照前后的膜蛋白巯基及膜氨基的变化,膜蛋白内源性荧光的变化,以及对膜蛋白形成交联的影响。结果表明:NEM、DEP和NBS修饰的膜, 在有甲素存在时,光照对巯基影响很小,而对SA修饰的膜有明显的光敏作用。甲素对膜蛋白氨基的影响小于巯基,仅降低含量20%。甲素光照能引起NEM和SA修饰的膜内源荧光下降。甲素对NEM处理的膜仍能引起交联,但SA处理过的膜能抗交联,说明氨基在膜蛋白光敏交联中起着重要的作用。     

葡萄糖淀粉酶色氨酸残基及底物结合位点的研究

 本文用N-溴代琥珀酰亚胺(NBS)对葡萄糖淀粉酶进行特异性修饰,当酶分子表面有3个色氨酸残基被修饰后,酶活力完全丧失。用邹氏图解法测得酶活性中心有一个色氨酸残基是必需的。如果在酶液中加入不同的底物再用NBS氧化,用荧光发射和荧光猝灭光谱检测表明,底物对酶分子有不同程度的保护作用。在被测试的三种底物中,这种保护能力依为糊精>淀粉>麦芽糖。     

毛花猕猴桃蛋白酶的提纯和性质

用硫酸铵盐析,磷酸盐除果胶和两次ＤＥＡＥ纤维素柱层析等方法,从毛花猕猴桃（ＡｃｔｉｎｉｄｉａｅｒｉａｎｔｈａＢｅｎｔｈ．）无细胞提取液中提纯蛋白酶,在聚丙烯酰胺凝胶电泳上呈现一条带,纯酶的活力为３２５Ｕ／ｍｇ,比活力提高８９倍,总收率约为３７％。用ＳＤＳ聚丙烯酰胺凝胶电泳测定分子量为２３ｋＤ,用等电聚焦电泳测定等电点为４８。酶的最适ｐＨ为３８,最适温度为４３℃左右。纯酶制剂对其底物牛血红蛋白的Ｋｍ值为５５６×１０－３ｍｍｏｌ。酶的紫外吸收光谱最大值为２７８ｎｍ。二巯基苏糖醇、巯基乙醇、Ｌ半胱氨酸盐酸盐等还原剂对该酶有明显的激活作用,而碘乙酸、对氯汞苯甲酸对其有抑制作用,这表明该酶属于巯基酶类。     

水稻巯基蛋白酶抑制剂的分子修饰与其对稻瘟病菌的抑制作用

水稻巯基蛋白酶抑制剂（ＣＰＩ）经用二硫苏糖醇,对氯汞苯甲酸和碘乙酸修饰后,对木瓜蛋白酶的抑制活性并无改变;用Ｎ－乙基顺丁烯二酰亚胺与ＣＰＩ反应,可以测出ＣＰＩ分子内有１９个巯基被修饰,被修饰后,抑制活性仍无改变,表明水稻ＣＰＩ的抑制活性不需要巯基参与;应用Ｎ－溴代丁二酰亚胺与ＣＰＩ反应,可测出ＣＰＩ分子内有２个Ｔｒｐ被修饰,修饰后,抑制活性全部丧失,表明Ｔｒｐ是保持抑制活性所必需的基团。水稻巯基蛋白酶抑制剂和丝氨酸蛋白酶抑制剂对稻瘟病菌丝体的生长均有抑制作用,但后者的抑制作用比前者更强,若将两种抑制剂混合使用,则对稻瘟病菌丝体的抑制作用非常强烈;当抑制剂加入量达７２μｇ时,即可产生明显的抑制作用。     

木瓜蛋白酶的研究 Ⅳ.活性中心组氨酸残基的羧甲基化

(1)在过量半胱氨酸存在下微量溴代乙酸或碘代乙酸在pH5对木瓜蛋白酶有強烈的抑制作用,当抑制剂与酶的克分子比为0.5时,抑制即达完全。抑制前后木瓜蛋白酶巯基含量不变。溴代乙酸作用后所得到的羧甲基木瓜蛋白酶汞盐結晶,与木瓜蛋白酶汞盐結晶相同。(2)在6M尿素溶液中溴代乙酸与木瓜蛋白酶的作用速度显著降低,底物L-白氨酰胺及抑制剂对氯汞苯甲酸都具有保护作用。这些事实表明溴代乙酸的抑制与木瓜蛋白酶的催化活性有密切关系,其作用点很可能是活性中心所在。(3)以双相电泳层析进行氨基酸組成分析結果指出,溴代乙酸作用点很可能是組氨酸殘基。     

背角无齿蚌碱性磷酸酶的功能基团研究

在一定条件下分别采用PMSF、DTT、PCMB、NBS、TNBS、SUAN、BrAc及IBr等化学修饰剂选择修饰背角无齿蚌碱性磷酸酶的多种氨基酸残基,并测定其酶活力变化。结果表明,PMSF、NBS、TNBS、SUAN、DTT的修饰能显著抑制酶的活力,活力的降低与修饰剂的浓度相关。BrAc、IAc、PCMB的修饰不表现对酶的抑制作用。作者初步认为,Ser、Lys和Trp残基是背角无齿蚌碱性磷酸酶的必需功能基团,部分二硫键时保护酶的催化功能也是必需的。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

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.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.