(2S,4S)-2,4-dimethyl-5-ketohexanoic acid | 1253642-74-8

• 分子结构分类: 有机化合物 - 脂质和类脂质分子 - 脂肪酰基
• 英文名称: (2S,4S)-2,4-dimethyl-5-ketohexanoic acid
• 英文别名: (2S,4S)-2,4-dimethyl-5-oxohexanoic acid
• CAS: 1253642-74-8
• 化学式: C₈H₁₄O₃
• 分子量: 158.197
• InChiKey: SPSSBFRNUFPFJQ-WDSKDSINSA-N

计算性质

• 辛醇/水分配系数(LogP)：
  0.9
• 重原子数：
  11
• 可旋转键数：
  4
• 环数：
  0.0
• sp3杂化的碳原子比例：
  0.75
• 拓扑面积：
  54.4
• 氢给体数：
  1
• 氢受体数：
  3

反应信息

• 作为产物：
  描述：

  2-methyl-3-ketobutyric acid-N-acetylcysteamine thioester 在 thioesterase 、 nanchangmycin synthase module 2 、 还原型辅酶II(NADPH)四钠盐 、 甲基丙二酰-辅酶A 作用下， 生成 (2S,4R)-2,4-dimethyl-5-oxohexanoic acid 、 (2S,4S)-2,4-dimethyl-5-ketohexanoic acid 、 4-hydroxy-3,5,6-trimethyl-2H-pyran-2-one
  参考文献：
  名称：

  Essential Role of the Donor Acyl Carrier Protein in Stereoselective Chain Translocation to a Fully Reducing Module of the Nanchangmycin Polyketide Synthase

  摘要：

  Incubation of recombinant module 2 of the polyether nanchangmycin synthase (NANS), carrying an appended thioesterase domain, with the ACP-bound substrate (2RS)-2-methyl-3-ketobutyryl-NANS_ACP1 (2-ACP1) and methylmalonyl-CoA in the presence of NADPH gave diastereomerically pure (25,4R)-2,4-dimethyl-5-ketohexanoic acid (4a). These results contrast with the previously reported weak discrimination by NANS module 2+TE between the enantiomers of the corresponding N-acetylcysteamine-conjugated substrate analogue (+/-)-2-methyl-3-ketobutyryl-SNAC (2-SNAC), which resulted in formation of a 5:3 mixture of 4a and its (2S,4S)-diastereomer 4h. Incubation of NANS module 2+TE with 2-ACP1 in the absence of NADPH gave unreduced 3,5,6-trimethyl-4-hydroxypyrone (3) with a K-cat of 4.4 +/- 0.9 min(-1) and a k(cat)/K-m of 67 min(-1) mM(-1), corresponding to a similar to 2300-fold increase compared to the k(cat)/K-m for the diffusive substrate 2-SNAC. Covalent tethering of the 2-methyl-3-ketobutyryl thioester substrate to the NANS ACP1 domain derived from the natural upstream PKS module of the nanchangmycin synthase significantly enhanced both the stereospecificity and the kinetic efficiency of the sequential polyketide chain translocation and condensation reactions catalyzed by the ketosynthase domain of NANS module 2.

  DOI：

  10.1021/bi201768v

文献信息

• Mechanism and Stereospecificity of a Fully Saturating Polyketide Synthase Module: Nanchangmycin Synthase Module 2 and Its Dehydratase Domain
  作者：Xun Guo、Tiangang Liu、Chiara R. Valenzano、Zixin Deng、David E. Cane

  DOI：10.1021/ja1073432

  日期：2010.10.27

  Recombinant nanchangmycin synthase module 2 (NANS module 2), with the thioesterase domain from the 6-deoxyerythronolide B synthase (DEBS TE) appended to the C-terminus, was cloned and expressed in Escherichia coli. Incubation of NANS module 2+TE with (+/-)-2-methyl-3-keto-butyryl-N-acetylcysteamine thioester (1), the SNAC analog of the natural ACP-bound substrate, with methylmalonyl-CoA (MM-CoA) in the absence of NADPH gave 3,5,6-trimethy1-4-hydroxypyrone (2), identified by direct comparison with synthetic 2 by radio-TLC-phosphorimaging and LC-ESI(+)-MS-MS. The reaction showed K(cat) 0.5 +/- 0.1 min(-1) and K(m)(1) 19 +/- 5 mM at 0.5 mM MM-CoA and k(cat)(app) 0.26 +/- 0.02 min(-1) and K(m)(MM-CoA) 0.11 +/- 0.02 mM at 8 mM 1. Incubation in the presence of NADPH generated the fully saturated triketide chain elongation product as a 5:3 mixture of (2S,4R)-2,4-dimethy1-5-ketohexanoic acid (3a) and the diastereomeric (2S, 4S)-3b. The structure and stereochemistry of each product was established by comparison with synthetic 3a and 3b by a combination of radio-TLC-phosphorimaging and LC-ESI(-)-MS-MS, as well as chiral capillary GC-MS analysis of the corresponding methyl esters 3a-Me and 3b-Me. The recombinant dehydratase domain from NANS module 2, NANS DH2, was shown to catalyze the formation of an (E)-double bond by syndehydration of the ACP-bound substrate anti-(2R,3R,4S,5R)-2,4-dimethyl-3,5-dihydroxyheptanoyl-ACP6 (4), generated in situ by incubation of (2S,3R)-2-methyl-3-hydroxypentanoyl-SNAC (5), methylmalonyl-CoA, and NADPH with the recombinant [KS6][AT6] didomain and ACP6 from DEBS module 6 along with the ketoreductase from the tylactone synthase module 1 (TYLS KR1). These results also indirectly establish the stereochemistry of the reactions catalyzed by the KR and enoylreductase (ER) domains of NANS module 2.
• Essential Role of the Donor Acyl Carrier Protein in Stereoselective Chain Translocation to a Fully Reducing Module of the Nanchangmycin Polyketide Synthase
  作者：Xun Guo、Tiangang Liu、Zixin Deng、David E. Cane

  DOI：10.1021/bi201768v

  日期：2012.1.31

  Incubation of recombinant module 2 of the polyether nanchangmycin synthase (NANS), carrying an appended thioesterase domain, with the ACP-bound substrate (2RS)-2-methyl-3-ketobutyryl-NANS_ACP1 (2-ACP1) and methylmalonyl-CoA in the presence of NADPH gave diastereomerically pure (25,4R)-2,4-dimethyl-5-ketohexanoic acid (4a). These results contrast with the previously reported weak discrimination by NANS module 2+TE between the enantiomers of the corresponding N-acetylcysteamine-conjugated substrate analogue (+/-)-2-methyl-3-ketobutyryl-SNAC (2-SNAC), which resulted in formation of a 5:3 mixture of 4a and its (2S,4S)-diastereomer 4h. Incubation of NANS module 2+TE with 2-ACP1 in the absence of NADPH gave unreduced 3,5,6-trimethyl-4-hydroxypyrone (3) with a K-cat of 4.4 +/- 0.9 min(-1) and a k(cat)/K-m of 67 min(-1) mM(-1), corresponding to a similar to 2300-fold increase compared to the k(cat)/K-m for the diffusive substrate 2-SNAC. Covalent tethering of the 2-methyl-3-ketobutyryl thioester substrate to the NANS ACP1 domain derived from the natural upstream PKS module of the nanchangmycin synthase significantly enhanced both the stereospecificity and the kinetic efficiency of the sequential polyketide chain translocation and condensation reactions catalyzed by the ketosynthase domain of NANS module 2.