ENZYMES OF THIAMIN METABOLISM

硫胺素代谢酶

• 批准号: 8361598
• 负责人: STEVEN E EALICK
• 金额: $ 1.14万
• 依托单位: CORNELL UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-04-01 至 2012-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8361598
• 关键词: Adenosine; Anabolism; Antimetabolites; Assimilations; Bacteria; Carboxylic Acids; Carrier Proteins; Cells; Clostridium botulinum; Couples; Coupling; DNA Sequence Rearrangement; Enzymes; Funding; Gene Cluster; Gram-Positive Bacteria; Grant; Human; Inorganic Sulfates; Iron; National Center for Research Resources; Pathway interactions; Phosphorylation; Plants; Principal Investigator; Proteins; Pyrimidine; Reaction; Research; Research Infrastructure; Resources; Ribonucleotides; Source; Structure; Sulfides; Sulfur; System; Thiamin Metabolism Pathway; Thiamine; Thiamine Pyrophosphate; Thiazoles; United States National Institutes of Health; Unspecified or Sulfate Ion Sulfates; Variant; Vitamins; Wolinella succinogenes; Yeasts; bacimethrin; cofactor; cost; inorganic phosphate; metabolic abnormality assessment; plant fungi; structural biology; thiamin phosphate synthase; thioester

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Thiamin pyrophosphate, the active cofactor form of vitamin B1 found within the cell, is an essential vitamin for humans. Although humans cannot biosynthesize this compound, most plants and bacteria are capable of producing thiamin. The pathways for thiamin biosynthesis vary between bacteria, which utilize a pathway with slight variations, and plants and fungi, which rely upon a different pathway. It is also possible for thiamin and degraded forms of thiamin to be salvaged. In fungal and plant systems, THI1 and THI4 respectively, are responsible for the formation of the thiazole precursor adenosine diphospho-5-(-ethyl)-4-methylthiazole-2-carboxylic acid. THI6, a bifunctional enzyme, catalyzes the phosphorylation of the thiazole moiety and couples the product of this reaction to the pyrimidine moiety to yield thiamin monophosphate. In yeast, THI20 is a second bifunctional enzyme that both hydrolyzes thiamin and phosphorylates the pyrimidine moiety. In bacteria, the thiazole and pyrimidine moieties are formed separately and then joined together relying on many enzymes. ThiE, thiamin phosphate synthase, is responsible for this coupling reaction. 4-Amino-5-hydroxymethyl-2-methylpyrimidine phosphate (HMP-P) synthase, or ThiC, is an iron-sulfur cluster protein responsible for the dramatic rearrangement of 5-aminoimidazole ribonucleotide (AIR) to form HMP-P. An important step in the biosynthesis of thiamin is the incorporation of an atom of sulfur into the growing thiazole moiety. In thiazole biosynthesis in bacteria, this is achieved by the activation of a sulfur carrier protein, ThiS, and the formation of a thioester at the carboxy terminus of ThiS in cooperation with a second protein, ThiF. Once the thioester has been formed on ThiS, the sulfur atom is then incorporated into the thiazole moiety via ThiG and ThiO/ThiH. Recently, a new sulfate assimilation pathway from Wolinella succinogenes has been identified, containing four enzymes which have primary structure similarity to the sulfur transfer enzymes of thiamin biosynthesis. These enzymes in W. succinogenes include a ThiS-like protein, a ThiF-like protein, a QBSD-like protein, and a putative O-acetylhomoserine sulfydrylase (OAHS), which might be involved in the transfer of sulfide to the activated WsThiS-like protein. In addition to enzymes of thiamin metabolism, we are studying an important toxic thiamin antimetabolite called bacimethrin. It is a molecule produced by some gram-positive bacteria that outcompetes the endogenous substrates of the thiamin biosynthetic pathway to produce a thiamin derivative. The gene cluster responsible for bacimethrin biosynthesis has been identified in Clostridium botulinum and the functions for each of these gene products has been confirmed.

该副本是利用资源的众多研究子项目之一 由NIH/NCRR资助的中心赠款提供。对该子弹的主要支持 而且，副投影的主要研究员可能是其他来源提供的 包括其他NIH来源。 列出的总费用可能 代表subproject使用的中心基础架构的估计量， NCRR赠款不直接向子弹或副本人员提供的直接资金。 硫胺素焦磷酸是细胞内的维生素B1的活性辅助形式，是人类必需的维生素。尽管人类无法生物合成这种化合物，但大多数植物和细菌都能产生硫胺素。硫胺素生物合成的途径在利用微小变化的途径以及依赖于不同途径的植物和真菌的细菌之间有所不同。硫胺素和退化的硫胺素形式也有可能被挽救。在真菌和植物系统中，Thi1和Thi4分别负责形成噻唑前体腺苷二磷-5-（ - 乙基）-4-甲基硫唑-2-羧酸。 Thi6是双功能酶，催化噻唑部分的磷酸化，并将这种反应的乘积与嘧啶部分相结合，从而产生硫胺素单磷酸盐。在酵母中，Thi20是第二个双功能酶，既能水解硫胺素并磷酸化嘧啶部分。 在细菌中，噻唑和嘧啶部分分别形成，然后依靠许多酶结合在一起。 Thie，硫代磷酸合酶，负责这种偶联反应。 4-氨基-5-羟基甲基-2-甲基苯二酰胺磷酸（HMP-P）合酶或THIC是一种铁硫簇蛋白，负责5-氨基氨基咪唑核糖核苷酸（空气）的急剧重排以形成HMP-P。 硫胺素生物合成的重要一步是将硫原子掺入生长的硫唑部分中。在细菌中噻唑的生物合成中，这是通过激活硫载体蛋白的激活来实现的，该硫磺蛋白以及与第二个蛋白质Thif合作，在该羧基末端的硫骨架形成。一旦在此形成硫酯后，将通过thig和thio/thih掺入硫原子中。 最近，已经鉴定出了来自Wolinella琥珀酸酯的新硫酸盐同化途径，其中包含四种与硫胺素生物合成的硫转移酶具有主要结构相似性的酶。 W.琥珀酸酯中的这些酶包括这种样的蛋白质，类似细菌的蛋白质，QBSD样蛋白和推定的O-乙酰基霍明氨基磺胺磺酰胺酶（OAHS），这些酶可能与硫化物转移到活化的WSTHIS样蛋白中有关。 除了硫胺素代谢的酶外，我们还研究了一种称为肉胆蛋白的重要有毒硫胺素抗代谢物。 这是某些革兰氏阳性细菌产生的分子，胜过硫胺素生物合成途径的内源性底物，产生硫胺素衍生物。 负责百麦米氧蛋白生物合成的基因簇已在肉毒梭菌中鉴定出来，并且已经证实了这些基因产物的每一种的功能。