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.

该子项目是利用资源的众多研究子项目之一 由 NIH/NCRR 资助的中心拨款提供。子项目的主要支持 并且子项目的首席研究员可能是由其他来源提供的， 包括其他 NIH 来源。 子项目可能列出的总成本 代表子项目使用的中心基础设施的估计数量， NCRR 赠款不直接向子项目或子项目工作人员提供资金。 焦磷酸硫胺素是细胞内维生素 B1 的活性辅助因子形式，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够产生硫胺素。硫胺素生物合成的途径在细菌和植物和真菌之间有所不同，细菌利用的途径略有不同，而植物和真菌则依赖不同的途径。硫胺素和硫胺素的降解形式也有可能被回收。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酸-5-(-乙基)-4-甲基噻唑-2-羧酸。 THI6 是一种双功能酶，催化噻唑部分的磷酸化，并将该反应的产物与嘧啶部分偶联，产生单磷酸硫胺素。在酵母中，THI20 是第二种双功能酶，可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，然后依靠许多酶连接在一起。 ThiE（硫胺素磷酸合酶）负责这种偶联反应。 4-氨基-5-羟甲基-2-甲基嘧啶磷酸 (HMP-P) 合酶 (HMP-P) 合酶 (ThiC) 是一种铁硫簇蛋白，负责 5-氨基咪唑核糖核苷酸 (AIR) 的剧烈重排形成 HMP-P。 硫胺素生物合成的一个重要步骤是将硫原子掺入不断生长的噻唑部分。在细菌的噻唑生物合成中，这是通过激活硫载体蛋白 ThiS 并在 ThiS 的羧基末端与第二种蛋白 ThiF 配合形成硫酯来实现的。一旦硫酯在 ThiS 上形成，硫原子就会通过 ThiG 和 ThiO/ThiH 掺入噻唑部分。 最近，从Wolinella succinogenes中鉴定出一条新的硫酸盐同化途径，该途径包含四种酶，其一级结构与硫胺素生物合成的硫转移酶具有相似性。 W. succinogenes 中的这些酶包括 ThiS 样蛋白、ThiF 样蛋白、QBSD 样蛋白和推定的 O-乙酰高丝氨酸磺化酶 (OAHS)，后者可能参与硫化物向活化的 WsThiS 的转移。像蛋白质。 除了硫胺素代谢酶外，我们还在研究一种重要的有毒硫胺素抗代谢物，称为杆菌肽。 它是由一些革兰氏阳性细菌产生的分子，它能与硫胺素生物合成途径的内源底物竞争，产生硫胺素衍生物。 肉毒梭菌中负责杆菌肽生物合成的基因簇已被鉴定，并且这些基因产物的功能均已得到证实。