14925-93-0Relevant academic research and scientific papers
Discovery and Engineering of Pathways for Production of α-Branched Organic Acids
Blaisse, Michael R.,Dong, Hongjun,Fu, Beverly,Chang, Michelle C. Y.
, p. 14526 - 14532 (2017/10/24)
Cell-based synthesis offers many opportunities for preparing small molecules from simple renewable carbon sources by telescoping multiple reactions into a single fermentation step. One challenge in this area is the development of enzymatic carbon-carbon bond forming cycles that enable a modular disconnection of a target structure into cellular building blocks. In this regard, synthetic pathways based on thiolase enzymes to catalyze the initial carbon-carbon bond forming step between acyl coenzyme A (CoA) substrates offer a versatile route for biological synthesis, but the substrate diversity of such pathways is currently limited. In this report, we describe the identification and biochemical characterization of a thiolase-ketoreductase pair involved in production of branched acids in the roundworm, Ascaris suum, that demonstrates selectivity for forming products with an α-methyl branch using a propionyl-CoA extender unit. Engineering synthetic pathways for production of α-methyl acids in Escherichia coli using these enzymes allows the construction of microbial strains that produce either chiral 2-methyl-3-hydroxy acids (1.1 ± 0.2 g L-1) or branched enoic acids (1.12 ± 0.06 g L-1) in the presence of a dehydratase at 44% and 87% yield of fed propionate, respectively. In vitro characterization along with in vivo analysis indicates that the ketoreductase is the key driver for selectivity, forming predominantly α-branched products even when paired with a thiolase that highly prefers unbranched linear products. Our results expand the utility of thiolase-based pathways and provide biosynthetic access to α-branched compounds as precursors for polymers and other chemicals.
Mechanism and stereospecificity of a fully saturating polyketide synthase module: Nanchangmycin synthase module 2 and its dehydratase domain
Guo, Xun,Liu, Tiangang,Valenzano, Chiara R.,Deng, Zixin,Cane, David E.
supporting information; scheme or table, p. 14694 - 14696 (2011/01/07)
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-trimethyl-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 Km(1) 19 ± 5 mM at 0.5 mM MM-CoA and kcat(app) 0.26 ± 0.02 min-1 and Km(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-dimethyl-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 syn-dehydration 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.
The thioesterase domain from the pimaricin and erythromycin biosynthetic pathways can catalyze hydrolysis of simple thioester substrates
Sharma, Krishna K.,Boddy, Christopher N.
, p. 3034 - 3037 (2008/02/05)
The recombinant polyketide synthase thioesterase domains from the pimaricin and 6-deoxyerythronolide B biosynthetic pathways catalyze hydrolysis of a number of simple N-acetylcysteamine thioester derivatives. This study demonstrates that thioesterases are not highly substrate selective in formation of the acyl-enzyme intermediate, in contrast to non-ribosomal peptide synthase thioesterase domains that show very high specificity for substrate loading. This observation has important implications for the engineering of biosynthetic pathways to produce polyketide products.
Carboxylation of Ketones Using Triethylamine and Magnesium Halides
Tirpak, Robin E.,Olsen, Richard, S.,Rathke, Michael W.
, p. 4877 - 4879 (2007/10/02)
Procedures for the carboxylation of ketones with carbon dioxide at atmospheric pressure in the presence of magnesium halides and triethylamine are described.A variety of ketones are converted to the corresponding β-keto acids in satisfactory yields by using magnesium chloride-sodium iodide mixtures in acetonitrile.This carboxylation reaction exhibits little regioselectivity with 2-butanone.
