Arthrobacter K1108乙内酰脲酶反应条件和立体选择性研究

研究了ArthrobacterK110 8乙内酰脲酶的反应条件 ,结果表明 ,K1108乙内酰脲酶的最适反应温度为 55℃ ,最适pH为 70 ,Co²⁺ 和Fe²⁺ 对该酶有激活作用 ,而Ca²⁺ 有严重抑制作用。K1108乙内酰脲酶的底物专一性较强 ,其最适底物为 5 苄基乙内酰脲 ,5 苯基乙内酰脲和 5 吲哚甲基乙内酰脲均不能作为其有效底物。对K1108乙内酰脲酶立体反应机制研究结果表明 ,其乙内酰脲水解酶不具立体选择性 ,决定产物立体构型的酶是N 氨甲酰氨基酸水解酶。     

AMP对蛇肌果糖-1,6-二磷酸酯酶pH9.2活力的激活作用——蛋白水解酶限制性酶解作用不是果糖-1,6-二磷酸酯酶变成碱性酶的唯一原因

低纯度的NADP⁺ 中含有一种在pH 9.2能够激活蛇肌果糖- 1 ,6 -二磷酸酯酶活力的物质 .经过分离鉴定 ,证明它就是 5′- AMP .该激活作用只有当较高浓度的Mg ²⁺ 存在时才表现出来 .在AMP的存在下 ,果糖 -1 ,6 -二磷酸酯酶的行为很像碱性酶 .Mg ²⁺ 激活动力学表明 ,AMP和Mg ²⁺ 在对蛇肌酶活力调节上存在着竞争关系 .AMP能解除高浓度Mg ²⁺对酶在碱性pH活力的抑制作用 .以往认为果糖- 1 ,6 -二磷酸酯酶由中性酶变成碱性酶均是由蛋白水解酶限制性酶解引起的 ;现报道 5′- AMP也能将蛇肌酶变成碱性酶 ,指出蛋白水解酶限制性酶解作用不是造成该酶由中性酶变为碱性酶的唯一原因 ,并且也可能有生理调节作用 .     

Sinorhizobium morelensS-5中N_氨甲酰基水解酶基因的克隆、表达和纯化

N_氨甲酰基水解酶是一种非常具有工业应用价值的水解酶,可用于制备光学纯氨基酸。通过LA PCR 从 Sinorhizobium morelens S_5 菌中克隆到13kb的DNA片段,测序表明该片段上含有一个完整的N_氨甲酰基水解酶的基因（hyuC）序列。将hyuC基因克隆到表达载体pET30a上,重组质粒pET30a_HyuC在大肠杆菌中获得了高水平表达。重组的N_氨甲酰基水解酶经过热处理和三步柱色谱分离而纯化。纯化倍数为16.1倍,收率21.2%。该酶为同源四聚体,亚基分子量是38kDa。最适温度是60℃,最适pH为7.0。该酶有较高的热稳定性和氧化稳定性。Fe²⁺和Ca²⁺对酶的活性有一定的促进作用,而金属螯合剂和巯基试剂对酶活无明显影响。     

氧化铝为载体的固定化葡萄糖异构酶某些性质的研究

本文报道了以廉价的大孔氧化铝作为葡萄糖异构酶的固定化载体。该固定化酶的热稳定性是60—70℃,如高于70℃就开始失活。最适Ph和温度分别为7．2—8．0和70℃。Gu²⁺、Fe²⁺、Zn²⁺、Mn²⁺和Ba²⁺等金属离子对它的酶活有抑制作用,Co²⁺和Mg²⁺金属离子却有明显的激活作用。该固定化酶酶活是6000—7000μ／g。通过柱运转,它的半衰期为40天以上,转化率是葡萄糖异构为果糖理论值的80一85％。     

假单胞菌株K9510产肌酐酰氨基水解酶的条件*

肌酐酰氨基水解酶是酶法分析血清肌酐浓度的关键酶。本实验室从空气中分离到能分解肌酐 的菌株 Ｋ９５１０、Ｋ９５１１和 Ｋ９５１２,其中Ｋ９５１０菌株初步分类鉴定为假单胞菌（Ｐｓｅｕｄｏｍｏｎａｓ ｓｐ.）。菌株 产酶条件优化研究结果表明：菌株在底物或底物类似物的诱导下产酶;混合金属离子溶液对菌株产 酶有促进作用。菌株产肌酐酰氨基水解酶最适培养基组成为：肌酐９ｇ、酵母提取物１．５ｇ、麦芽汁０．９ｇ、 ＮＨ_４Ｃｌ０． ５ｇ、定容 １Ｌ。适量混合金属离子溶液,用 ０． １ｍｏｌ     

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。     

海藻糖酶产生菌的选育、鉴定及其酶学特性初探

海藻糖酶可特异性将1分子海藻糖分解为2分子葡萄糖,在乙醇工业、食品等行业中具有广阔的应用前景。从环境土壤中筛选到1株海藻糖酶产生菌C2,根据形态学分析和分子生物学鉴定将其命名为大黄欧文氏菌（Erwinia rhapontici）。该菌株产海藻糖酶的最适温度为40 ℃,最适pH为5.0,在酸性及低于35 ℃条件下,该酶具有较高的稳定性,Ca²⁺、Zn²⁺、Ni²⁺、Mn²⁺、Cu²⁺、K⁺、Na⁺和Fe²⁺对海藻糖酶酶活具有促进作用,DMSO和DTT对酶活具有一定的提升作用,而Triton X-114、SDS和PMSF则对酶活具有抑制作用。     

MehpH的生化与结构特性

[目的]本研究旨在系统探究环境因素对邻苯二甲酸单乙基己基酯水解酶（monoethylhexyl phthalate hydrolase,MehpH）活性的影响,模拟该酶的3D结构并分析活性中心氨基酸残基与底物之间的相互作用。[方法]根据标准的酶学实验验证了环境因素对酶活性的影响。该酶的基本结构分析由DNAMAN （2.1）分析所得,同时利用SWISS-MODEL对其3D模型进行预测,并通过PyMOL软件对相关结果作了可视化处理。Autodock工具,Swiss-Pdb以及PyMOL均用以酶与邻苯二甲酸单乙基己基酯（monoethylhexyl phthalate,MEHP）的相互作用分析。[结果]该酶的初级结构与已报道Gordonia sp. P8219菌株中的酯类水解酶相似,该酶的最适温度与pH （分别为40℃和8.0）和菌株P8219有所不同;该酶在有机溶剂、洗涤剂和金属离子环境中表现出良好的稳定性;然而,其酶活受2 mol/L的Ni²⁺、Fe³⁺、Cu²⁺和Zn²⁺离子,1 mol/L苯甲基磺酰氟（PMSF）,0.5 mol/L的对氧磷,1 mol/L苯基醚（PGO）,2 mol/L焦碳酸二乙酯（DEPC）和5 mol/L的毒扁豆碱所抑制。丝氨酸水解酶中高度保守五肽基序GXSXG与催化三联体HSD结构均存在于该酶的编码序列中。根据分子对接结果,Thr152与Ser230在水解酶与其模板之间也显得更为保守,且与MEHP联系较为紧密（分别为5.8 Å和3.6 Å）,可能起着重要的催化作用。而MEHP与催化氨基酸残基Ser125、His291、Asp259并不十分靠近。[结论]YC-RL2中MehpH在有机溶剂、洗涤剂以及金属离子环境中具有稳定的生物活性,表明其具有良好的应用潜力。酶的结构及活性中心得到了初步的分析,对于催化机理及酶改造研究具有重要意义。     

兔肌3-磷酸甘油脱氢酶的提纯及性质研究

目的:研究兔肌3-磷酸甘油脱氢酶的分离纯化方法及其酶学性质,为测定血清甘油三酯所用酶联试剂的开发提供试验基础和理论依据。方法:通过硫酸铵分级沉淀、DEAE-Sepharose、Blue-Sepharose和羟磷灰石纯化兔肌3-磷酸甘油脱氢酶,利用凝胶过滤和梯度PAGE(5%～15%)法测定酶分子量,采用常规酶学动力学分析方法,考察pH、温度、底物浓度以及部分金属离子与有机化合物对酶促反应的影响。结果 纯化后的兔肌3-磷酸甘油脱氢酶经PAGE(12%)分析为单一条带;酶分子量为115～122 kDa;酶最适温度45℃,最适pH 9;酸碱稳定范围pH6～9,低于45℃时热稳定性好;最适条件下,以3-磷酸甘油和NAD⁺为底物,测得酶的K_m分别为7.4×10^-3mol/L和1.47×10^-4mol/L;Ba²⁺、Mn²⁺、Fe²⁺、Al³⁺、Cu²⁺、Ni²⁺、Ag⁺、Hg²⁺、NaN₃、EDTA对酶有不同程度的抑制作用,Mg²⁺、Ca²⁺、Co²⁺、Zn²⁺有一定程度的激活作用,其中Co²⁺和Zn²⁺对酶的激活作用能达到200%以上,有机化合物NaF对酶的活性没有影响。     

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-     

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.     

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.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.