透明质酸酶的研究进展

透明质酸酶是能降解透明质酸及部分糖胺聚糖的一类糖苷酶,可应用于医疗和美容等领域。透明质酸酶也可用于制备小分子糖胺寡糖,许多研究发现小分子糖胺寡糖具有比大分子糖胺聚糖更高的生物免疫活性。为便于研究人员对透明质酸酶进行进一步的基础研究及应用研究,本文介绍了透明质酸和透明质酸酶,梳理了透明质酸酶的分类、结构和催化机理,归纳总结了透明质酸酶的酶活力测定方法、重组表达、酶学性质和应用,展望了透明质酸酶的研究方向。     

透明质酸生物合成途径及基因工程研究进展

透明质酸是由N-乙酰氨基葡萄糖和葡萄糖醛酸组成的双糖单位聚合而成的直链酸性黏多糖,已被广泛应用于药物、化妆品和食品添加剂。微生物发酵法是目前生产透明质酸最有效的方法。生物体内透明质酸的合成途径基本一致,均为Leloir途径。透明质酸合成操纵子由透明质酸合酶基因、尿苷二磷酸葡萄糖脱氢酶基因和尿苷二磷酸葡萄糖焦磷酸化酶基因组成,其表达受Cov S/CovR和Lux S等多种调控系统调控。随着分子生物学技术的迅速发展以及对透明质酸合成相关基因了解的不断深入,人们从提高透明质酸安全性、提高透明质酸产量和调控透明质酸分子质量三个方面出发,通过基因工程手段构建出了高产、安全、一定分子质量范围的透明质酸生产菌株。就有关透明质酸生物合成途径、合成相关基因表达调控及生产菌株分子生物学改造的策略与研究进展进行综述和展望。     

透明质酸酶的研究进展

透明质酸酶是以降解透明质酸为主的糖苷酶。近年来国内外关于透明质酸酶各方面的研究日益增多,透明质酸酶的构效关系及生物学应用越来越引起人们的关注。对透明质酸酶的相关研究进行了综述,主要阐述了各类型透明质酸酶的研究概况包括人透明质酸酶、牛睾丸透明质酸酶、毒液透明质酸酶、微生物透明质酸酶。简要介绍了透明质酸酶的活性测定、酶活抑制剂及透明质酸酶制剂的应用情况,最后对透明质酸酶的研究前景进行展望。     

天然产物中透明质酸酶抑制剂的研究

透明质酸酶抑制剂是对透明质酸酶的激活有抑制作用的物质。透明质酸酶是透明质酸的特异性裂解酶,而透明质酸在人体许多发育和调控过程中起重要作用,抑制透明质酸酶的活性可使透明质酸不被分解,维持正常的生理功能,笔者对天然产物中透明质酸酶抑制的研究开发进行了概述,并探讨了透明质酸酶抑制在医药及保健食品工业中的应用潜力。     

微生物发酵法生产高分子量透明质酸的研究进展

透明质酸是一种线性大分子黏多糖,分子量定义其流变性能,影响生理反应,并决定合适的用途。传统研究通过优化发酵提高透明质酸的产量已取得显著成效,近年来,研究重点逐渐转向如何提高透明质酸产品的分子量。目前,高分子量透明质酸具有良好的黏弹性、保湿性、黏附性,在医药中的应用是中、低分子量透明质酸不可替代的。概述了透明质酸分子量的调控机制,以及利用微生物发酵法生产高分子量透明质酸的研究进展,并对其发展方向进行了展望。     

微生物发酵法生产透明质酸

透明质酸(Hyaluronic acid,以下简称HA)是一种高分子粘多糖,具有良好的亲水性、生物相容性和保湿功能,广泛应用于食品、化妆品和医药领域.透明质酸的传统生产方法是主要从动物组织中提取,用微生物发酵法生产透明质酸正逐步取代传统生产方法,其优点是原料易得、成本低、所产透明质酸有更高的产量和分子量等原因.     

透明质酸生产菌溶血素S基因缺失突变菌株的构建及其特性北大核心CSCD

【目的】马链球菌兽疫亚种是工业上生产透明质酸的主要菌种,该菌能产生引起宿主细胞溶血的链球菌溶血素S(streptolysin S,SLS)毒素,因而其产品的安全性一直是人们所担心的问题。本实验的目的就是通过基因敲除的方法构建不产SLS的透明质酸生产工程菌,同时探讨溶血素sag A基因缺失对菌株透明质酸合成和其他毒力因子的影响。【方法】利用温度敏感/自杀性质粒p JR700载体系统,构建马链球菌兽疫亚种sag A基因缺失突变株;通过PCR扩增,溶血平板和SLS含量测定等方法确定sag A基因缺失;采用分光光度、SDS-PAGE和细胞毒性试验等分析方法,对野生菌株和sag A基因缺失突变菌株透明质酸含量、透明质酸分子量、溶血素Hylc、透明质酸分解酶、甘油醛-3-磷酸脱氢酶和菌体表面蛋白等相关毒力因子进行对比研究。【结果】获得了透明质酸产量提高30%而溶血活性极低的马链球菌兽疫亚种sag A基因缺失突变株。该突变株与野生菌株相比较,透明质酸分解酶活性增加而透明质酸相对分子量降低,此外,与毒力相关的表面蛋白含量、溶血素Hylc和甘油醛-3-磷酸脱氢酶活性也显著降低。细胞毒性实验结果表明,野生菌株与sag A基因缺失突变菌株的培养物上清液,对细胞活性的影响存在显著差异。【结论】在马链球菌兽疫亚种中sag A不仅是表达溶血素SLS的基因,同时sag A基因对菌株透明质酸合成、透明质酸分解酶、菌体表面蛋白、溶血素Hylc和甘油醛-3-磷酸脱氢酶等都具有调节作用。     

高产透明质酸菌种FJ-23的诱变选育

目的:高产透明质酸菌种的选育是提高透明质酸产量和质量的关键。方法:以马疫链球菌SH-0为出发菌,对其进行紫外诱变和NTG诱变选育。结果:筛选出溶血素和透明质酸酶双缺陷型突变菌株FJ-23,其透明质酸产量提高了7倍;突变株经6次传代,其产酸量及HA的相对分子量保持稳定,为今后进一步研究发酵法生产透明质酸打下基础。     

交联透明质酸衍生物的研究进展

交联透明质酸既保持了天然透明质酸的生物特性,又弥补了天然透明质酸宜分解不稳定的缺陷,因此交联透明质酸可作为医疗、美容和组织工程领域的新型材料进一步扩展研究。主要针对国内外对制备交联透明质酸的各种交联剂进行了介绍,为研究新型透明质酸衍生物提供选择。     

链球菌合成透明质酸的研究进展

透明质酸是一种具有极大商业价值的线性、高分子粘多糖,微生物的生物合成是透明质酸来源的首选。主要综述链球菌合成透明质酸的研究概况,分析了目前存在的主要问题及解决途径,并对其前景进行了展望。     

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.