Taxonomy of Aureobasidium spp. and biosynthesis and regulation of their extracellular polymers

Abstract

The genus Aureobasidium spp. have been divided into three species, A. pullulans. A. leucospermi and A. proteae, and A. pullulans has been known to have five varieties. However, after analysis of many strains of this yeast isolated from different environments, they do not belong to any of the three species or the five varieties. Although pullulan produced by A. pullulans has been widely used in different fields in industry and different strains of this yeast has been known to produce poly(β-L-malic acid) (PMA), heavy oils and β-1,3-glucan, it is still unknown how the black yeast synthesizes and secretes the extracellular polymers at molecular level. In this review article, new biosynthetic pathways of pullulan, PMA and heavy oils, the enzymes and their genes related to their biosynthesis and regulation are proposed. Furthermore, some enzymes and their genes related to pullulan biosynthesis in A. pullulans have been characterized. But it is completely unknown how pullulan is secreted and how PMA, heavy oils and β-1,3-glucan are synthesized and secreted. Therefore, there is much work to be done about taxonomy and biosynthesis, secretion and regulation of pullulan, PMA, heavy oils and β-1,3-glucan at molecular levels in Aureobasidium spp.     

S100A4在大肠腺瘤和大肠癌中表达的临床病理研究

目的探讨S100A4蛋白在大肠腺瘤和大肠癌组织中的表达及其临床病理意义。方法应用免疫组化S-P法检测51例大肠腺瘤,87例大肠癌组织及癌旁大肠组织中S100A4蛋白的表达情况。结果在癌旁大肠组织腺上皮中S100A4蛋白不表达;在大肠腺瘤组织中S100A4蛋白的表达率为11.8(6/51);在大肠癌组织中S100A4蛋白的表达率为64.4(56/87);与癌旁大肠组织、大肠腺瘤组织比较,差异有显著性(P<0.01);S100A4蛋白在大肠癌中的表达与临床分期、淋巴结转移及5年生存率有关(P<0.05),与其它临床病理因素无关(P>0.05)。结论S100A4蛋白可能在大肠癌发生、发展中发挥作用,尤其在大肠癌恶性演进中以及预后预测中具有重要意义,可能作为新的生物标志物。     

A comparative study of Florida strains of Cylindrospermopsis and Aphanizomenon for cylindrospermopsin production.

The toxin cylindrospermopsin (CYN) is produced by a variety of cyanobacterial genera. One of these, Cylindrospermopsis raciborskii, is generally assumed to be the source of CYN in lakes and rivers in Florida, USA. However, in this study, none of the eight Florida isolates of this species tested contained the genetic determinants involved in toxin production nor did they produce CYN. We show for the first time that Aphanizomenon ovalisporum isolated from a pond in this state has the genes putatively associated with CYN production. Analysis by liquid chromatography with mass spectrometric detection (LC/MS) revealed that it produced CYN in the range of 7.39-9.33 microg mg(-1) freeze-dried cells. 16S rDNA sequences of this strain showed 99.6% and 99.9% identity to published A. ovalisporum and Anabaena bergii 16S sequences, respectively. These results help to explain the general lack of a defined relationship between the abundance of C. raciborskii in freshwater ecosystems of Florida and observed concentrations of CYN. The latter observation raises the potential that previous reports of CYN may be coincidental with unrecorded presence of another CYN-producing species.     

新抗菌靶点肽去甲酰基酶抑制剂的研究进展

综述新抗菌靶点肽去甲酰基酶在细菌蛋白合成中的作用、三维结构及其抑制剂的设计、发现与开发和耐药菌的产生。随着细菌耐药性的广泛发生以及多药耐药菌的出现,临床上急需对耐药菌有效的新型抗菌药,而寻找新型抗菌靶点为抗耐药菌药物的研究提供了新思路。     

突变生物合成在微生物药物领域的研究进展

突变生物合成作为产生抗生素衍生物的重要手段，自20世纪70年代兴起以来，发挥了巨大作用，已开发出许多至今在临床上仍广泛使用的抗生素品种。随着基因技术的发展．突变生物合成技术可直接对次级代谢途径中一特定酶基因进行改造获得突变株．大大提高了工作效率和准确性。本文综述了突变生物合成技术在微生物药物领域的应用，特别是结合基因技术进行突变生物合成研究的新进展。     

EXPRESSION OF c－myc GENE AND BIOSYNTHESIS OF BIOLOGICAL MACROMOLECULES IN ANTISENSE TRANSFECTANT HL_（60）~R－9

ＥＸＰＲＥＳＳＩＯＮＯＦｃ－ｍｙｃＧＥＮＥＡＮＤＢＩＯＳＹＮＴＨＥＳＩＳＯＦＢＩＯＬＯＧＩＣＡＬＭＡＣＲＯＭＯＬＥＣＵＬＥＳＩＮＡＮＴＩＳＥＮＳＥＴＲＡＮＳＦＥＣＴＡＮＴＨＬ_（６０）~Ｒ－９ＬｉＹｉｎｘｉｏｎｇ李尹雄，ＦａｎＭｕｚｈｅｎ范慕贞，Ｚｈａ...     

Tetrahydrobiopterin deficiency: assay for 6-pyruvoyl-tetrahydropterin synthase activity in erythrocytes,and detection of patients and heterozygous carriers

6-Pyruvoyl-tetrahydropterin synthase (PTS), a key enzyme in the synthesis of tetrahydrobiopterin in man, is defective in the most frequent variant of tetrahydrobiopterin-deficient hyperphenylalaninaemia (atypical phenylketonuria). An assay for PTS activity in erythrocytes was developed. It is based on the PTS-catalysed formation of tetrahydrobiopterin from dihydroneopterin triphosphate in the presence of magnesium, sepiapterin reductase, NADPH, dihydropteridine reductase, and NADH, and fluorimetric measurement of the product as biopterin by high performance liquid chromatography (HPLC) after oxidation with iodine. The PTS activity was higher in younger erythrocytes, including reticulocytes, than in older ones. Fetal erythrocytes showed approx. four times higher activities than those of adults. Using a more purified human liver sepiapterin reductase fraction which gave a lower yield than a crude preparation, adult controls (n=8) showed a mean erythrocyte PTS activity of 17.6 (range 11.0–29.5) U/g Hb. Nine of 11 patients with typical PTS deficiency showed activities between 0% and 8% of the mean of controls, and two of 11 showed 14% and 20%, respectively. The obligate heterozygotes (n=16) had activities of 19% (range 8%–31%) of the mean of controls, i.e., significantly less than the expected 50%. Four patients with the peripheral type of the disease showed 7%–10% of the mean of controls. Thus, the assay did not distinguish between patients and heterozygotes in every family. The assay is well suited to the identification of heterozygotes of PTS deficiency in family studies.Abbreviations DHPR dihydropteridine reductase - HPLC high-performance liquid chromatography - PTS 6-pyruvoyl-tetrahydropterin synthase Professor Niederwieser has unfortunately died since the paper was accepted     

微生物次级代谢产物生物合成基因簇与药物创新

微生物产生众多结构和生物活性多样的次级代谢产物，其生物合成基因簇的克隆是药物创新和产量提高的必要前提。迄今为止已有超过150种生物合成基因簇通过各种方式被克隆，并被用于组合生物合成、体外糖类随机化、代谢工程的定向改造。我们研究室已经克隆并测定了氨基糖苷类井冈霉索／有效霉索、多烯类抗生素FR-008／克念菌索、聚醚类南昌霉索、聚酮类梅岭霉索、杂合聚酮一多肽类略唑霉索等生物合成基因簇。深入的基因功能分析揭示了他们独特的生物合成途径和调节机理，为正在进行的组合生物合成结构改造和代谢工程产量提高奠定了基础。     

聚酮合成酶底物专一性的研究进展

聚酮合成酶能够合成包括许多大环内酯类抗生索在内的聚酮类天然产物，它的结构和功能的模块性为组合生物合成的产生和发展奠定了基础。聚酮合成酶的酰基转移酶功能域可以特异性地决定所选择酰基辅酶A的种类．决定产物的结构。近年来，针对许多来源不同、结构各异的聚酮合成酶的底物专一性已经从氨基酸序列、结构和功能等方面进行了大量的研究．为更有效地应用聚酮合成酶开发新型抗生索奠定了基础。     

血管内皮生长因子与抑癌基因PTEN在肝细胞癌组织中表达及临床意义

目的:观察第10号染色体上缺失与张力蛋白同源的磷酸酯酶基因(phosphatase and tensinhomlog deleted on chromosome ten protein,PTEN)和血管内皮生长因子(vascular endothelial growthfactor,VEGF)在肝细胞癌(hepatocellular carcino-ma,HCC)中表达及其关系,并探讨两者与HCC发生、发展及肿瘤侵袭性的关系。方法:采用免疫组织化学链霉素亲合素-生物素-过氧化物酶复合物(SP)法、半定量逆转录-聚合酶链反应(RT-PCR)检测60例HCC及癌旁组织中PTEN与VEGF蛋白及mRNA表达和微血管密度(microvessel density,MVD),并进一步分析它们之间的相关性及其与肝癌组织临床病理分期、侵袭性的关系。结果:HCC中PTEN蛋白及mRNA表达阳性强度明显低于癌旁组织,而VEGF阳性表达强度明显高于癌旁组织,且两者间呈负相关(r=-0·613、-0·572,P=0·000、0·002);肝癌组织分化程度、侵袭性与PTEN表达呈负相关(P=0·02、0·000),而与VEGF和MVD表达呈正相关(P=0·000);MVD与PTEN表达呈负相关(r=-0·439,P=0·001),而与VEGF表达呈正相关(r=0·645,P=0·000)。结论:PTEN和VEGF表达水平一定程度上能反映HCC组织分化和侵袭性强弱;HCC中PTEN表达缺失可能引起VEGF表达增加,从而在肿瘤侵袭、转移中发挥一定作用。