白地霉的氧化代谢

1．自地霍完整静息幼胞氧化乙醇、乙酸、丙酮酸及草酰乙酸的速度很高,对其他三羧酸循环各酸如：琥珀酸、延胡索酸、a-酮戊二酸、苹果酸、柠檬酸、顺岛头酸及异柠檬酸也能氧化,但速度甚低。 2．在白地霉无细胞提取液中测出了三羧酸循环中以下各种酶活力：柠檬酸精合酶、异柠檬酸脱氢酶、顺岛头酸酶、a-酮戊二酸脱氢酶、琥珀酸脱氢酶、延胡索酸酶、苹果酸脱氢酶、苹果酸酶、草酰乙酸羧化酶等,并间接得知有乙酸激活酶及L-谷氨酸脱氢酶存在。 3．在白地霉无捆胞提取液中测出了乙醛酸循环的两个关键的酶皂口异柠檬酸酶及苹果酸合成酶。 4．由以上结果可知白地霉可利用三羧酸循环及乙醛酸循环作为末端呼吸途径。     

种子中异柠檬酸裂解酶活性的测定

油类种子在萌发过程中,通过脂肪酸的β-氧化和乙醛酸循环将脂肪酸转变成碳水化合物。在乙醛酸循环中,异柠檬酸裂解酶(Isocitrate lyase,简写成ICL)是关键酶之一。它催化异柠檬酸裂解成乙醛酸和琥珀酸,前者进入乙醛酸循环,后者通过一系列反应(主要是糖酵解的逆转)合成葡萄糖。因此,测     

细菌中2-甲基柠檬酸循环研究进展

2-甲基柠檬酸循环广泛分布于细菌中,参与丙酸或丙酰-CoA的分解代谢。我们一直致力于微生物代谢调控方面的研究,并以苏云金芽胞杆菌为研究对象在2-甲基柠檬酸循环的代谢调控及生理功能方面取得了新的进展。本文将从2-甲基柠檬酸循环关键酶基因的组成、关键酶基因的转录调控和该循环参与的生理功能3个方面介绍细菌中2-甲基柠檬酸循环的研究进展。同时,对该循环研究中存在的相关科学问题和未来的研究重点作简要评述,并对该循环关键酶作为药物靶标在病原菌感染防治方面的应用进行展望。     

一类新广谱抗生素药物靶标--异柠檬酸裂合酶的生物学研究

乙醛酸循环是一个重要的能量代谢途径,普遍存在于微生物体内,它在微生物致病过程中发挥了至关重要的作用。异柠檬酸裂合酶作为乙醛酸循环的第一个关键酶,是理想的抗感染药物靶标．了解该酶的基本结构性质、生物学功能及其分子生物学进展将有助于新型抗菌药物的开发。     

尿素对热带假丝酵母Candida tropicalis合成长链二元酸途径的调节 Ⅱ.几个关键酶活力的消长

前文已报道尿素及尿素结构类似物对长链二元酸的合成酶系既有抑制作用,也有阻遏作用,从而调节了长链二元酸的合成。本文进一步从离体酶系探索过量尿素对热带假丝酵母在烃类氧化过程中有关三羧酸循环,乙醛酸循环,呼吸链,ω和β氧化等几个关键酶活力的消长关系。实验结果证明,过量尿素(0.2%)以上培养菌体的三羧酸循环三个主要脱氢酶,苹果酸脱氢酶,琥珀酸脱氢酶和异柠檬酸脱氢酶(NADP)的比活力分别为正常尿素(0.1%)培养菌体的5.3、3.0、1.7倍。乙醛酸循环关键酶,异柠檬酸裂解酶和苹果酸合成酶分别为正常尿素培养物的2.6和2.8倍。另一方面当尿素过量时ω-氧化酶系活力极微,而β-氧化酶系活力大大提高,以致长链二元酸难以积累。另外过氧化氢酶活力在过量尿素存在时也有显著提高。而谷氨酸脱氢酶、NADH氧化酶和由NAD连结的异柠檬酸脱氢酶在两种菌体内无明显差别。     

尿素对热带假丝酵母Candida tropicalis合成长链二元酸途径的调节——Ⅱ.几个关键酶活力的消长

前文已报道尿素及尿素结构类似物对长链二元酸的合成酶系既有抑制作用,也有阻遏作用,从而调节了长链二元酸的合成。本文进一步从离体酶系探索过量尿素对热带假丝酵母在烃类氧化过程中有关三羧酸循环,乙醛酸循环,呼吸链,ω和β氧化等几个关键酶活力的消长关系。实验结果证明,过量尿素(0.2%)以上培养菌体的三羧酸循环三个主要脱氢酶,苹果酸脱氢酶,琥珀酸脱氢酶和异柠檬酸脱氢酶(NADP)的比活力分别为正常尿素(0.1%)培养菌体的5.3、3.0、1.7倍。乙醛酸循环关键酶,异柠檬酸裂解酶和苹果酸合成酶分别为正常尿素培养物的2.6和2.8倍。另一方面当尿素过量时ω-氧化酶系活力极微,而β-氧化酶系活力大大提高,以致长链二元酸难以积累。另外过氧化氢酶活力在过量尿素存在时也有显著提高。而谷氨酸脱氢酶、NADH氧化酶和由NAD连结的异柠檬酸脱氢酶在两种菌体内无明显差别。     

甘蓝型油菜子油分的积累与某些生理变化关系的研究

油菜种子发育过程中,其内部的生理代谢过程发生了规律性的变化。伴随着种子的发育进程,６－磷酸葡萄糖脱氢酶、异柠檬酸裂解酶、异柠檬酸脱氢酶和琥珀酸脱氢酶的活性均有不同程度的增强。在油分旺盛合成期,６－磷酸葡萄糖脱氢酶和异柠檬酸裂解酶的活性均达到了最大值,而此时,异柠檬酸脱氢酶和琥珀酸脱氢酶的活属于匀增加较慢;在种子的不同发育时期,高含油量品系的６－磷酸葡萄糖脱氢酶和异柠檬酸裂解酶的活性均高于低含油量的     

异柠檬酸脱氢酶在植物抗氧化胁迫中的作用

异柠檬酸脱氢酶(ICDH)是连接C-N代谢酶的关键,它催化三羧酸循环(TCA)中的异柠檬酸氧化脱羧形成α-酮戊二酸的可逆反应。ICDH的另一个重要功能是产生细胞质中的NADPH,NADPH在细胞中无处不在,介导许多氧化还原反应,并影响到几乎所有的代谢途径,涉及植物体内的活性氧(ROS)的生产和消耗,因此是传递胁迫信号的中转站。综述异柠檬酸脱氢酶在植物抗氧化胁迫中的作用,便于更好地理解ICDH在氧化胁迫中的信号传递和化学反应中所起的作用,为抗逆分子育种服务。     

钉螺柠檬酸代谢酶系及琥珀酸脱氢酶的初步研究

应用比色法测得钉螺体内有柠檬酸缩合酶、顺乌头酸酶及异柠檬酸酶的活力。新杀螺剂溴乙酰胺作用后,钉螺的柠檬酸缩合酶活力减低26％,而对顺乌头酸酶及异柠檬酸酶无影响。体外试验丙二酸及二乙基二硫代氨基甲酸钠都可抑制钉螺琥珀酸脱氢酶,而钉螺在后者2ppm的溶液中浸泡48小时,有90—100％的死亡。     

异柠檬酸脱氢酶2突变或诱导机体产生肉瘤

<正>线粒体内依赖辅酶NADP+的异柠檬酸脱氢酶2(IDH2)在新陈代谢中起重要作用,IDH2催化异柠檬酸脱氢生成α-酮戊二酸(αKG),参与三羧酸循环。而当其发生突变时,IDH2则催化异柠檬酸生成2-羟戊二酸(2HG),并竞争性抑制αKG的DNA-组蛋白脱甲基酶,导致细胞分化功能受损。美国宾夕法尼亚大学Lu等人通过全组基因甲基化水平测定,发现IDH2突变通过甲基化DNA CpG岛产生致癌作用,但     

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.