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Aldol Cleavage (aldol + cleavage)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

A Temporary Stereocentre Approach for the Stereodivergent Synthesis of Either Enantiomer of ,-Methyloctanal

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 33 2007
D. Gangani Niyadurupola
Abstract The aldol reaction of a chiral N -(acyl)oxazolidin-2-one with 2-methyleneoctanal or (E)-2-methyloct-2-enal affords chiral aldol products whose alkene functionalities were hydrogenated using Brown's or Wilkinson's catalyst to afford syn - or anti -selective products with excellent levels of diastereocontrol. Subsequent retro -aldol cleavage of these syn - or anti -adducts resulted in the formation of either (R)- or (S)-enantiomer of ,-methyloctanal with no racemisation occurring, which could be derivatised in-situ to afford chiral dithiane, alcohol or ,,,-unsaturated ester products in enantiopure form.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

Structure of human brain fructose 1,6-(bis)phosphate aldolase: Linking isozyme structure with function

PROTEIN SCIENCE, Issue 12 2004
Tracy L. Arakaki
Abstract Fructose-1,6-(bis)phosphate aldolase is a ubiquitous enzyme that catalyzes the reversible aldol cleavage of fructose-1,6-(bis)phosphate and fructose 1-phosphate to dihydroxyacetone phosphate and either glyceral-dehyde-3-phosphate or glyceraldehyde, respectively. Vertebrate aldolases exist as three isozymes with different tissue distributions and kinetics: aldolase A (muscle and red blood cell), aldolase B (liver, kidney, and small intestine), and aldolase C (brain and neuronal tissue). The structures of human aldolases A and B are known and herein we report the first structure of the human aldolase C, solved by X-ray crystallography at 3.0 Å resolution. Structural differences between the isozymes were expected to account for isozyme-specific activity. However, the structures of isozymes A, B, and C are the same in their overall fold and active site structure. The subtle changes observed in active site residues Arg42, Lys146, and Arg303 are insufficient to completely account for the tissue-specific isozymic differences. Consequently, the structural analysis has been extended to the isozyme-specific residues (ISRs), those residues conserved among paralogs. A complete analysis of the ISRs in the context of this structure demonstrates that in several cases an amino acid residue that is conserved among aldolase C orthologs prevents an interaction that occurs in paralogs. In addition, the structure confirms the clustering of ISRs into discrete patches on the surface and reveals the existence in aldolase C of a patch of electronegative residues localized near the C terminus. Together, these structural changes highlight the differences required for the tissue and kinetic specificity among aldolase isozymes. [source]

Preliminary crystallographic studies of an extremely thermostable KDG aldolase from Sulfolobus solfataricus

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 11 2000
Elaine J. Hendry
Crystals have been grown of 2-keto-3-deoxygluconate aldolase (KDG aldolase) from the hyperthermophilic archaeon Sulfolobus solfataricus that diffract to 2.2,Å resolution. The enzyme catalyses the reversible aldol cleavage of 2-keto-3-dexoygluconate to pyruvate and glyceraldehyde, the third step of a modified non-phosphorylated Entner,Doudoroff pathway of glucose oxidation. S. solfataricus grows optimally at 353,K and the enzyme itself has a half-life of 2.5,h,at 373,K. Knowledge of the crystal structure of KDG aldolase will further understanding of the basis of protein hyperthermostability and create a target for site-directed mutagenesis of active-site residues, with the aim of altering substrate specificity. Three crystal forms have been obtained: orthorhombic crystals of space group P212121, which diffract to beyond 2.15,Å, monoclinic crystals of space group C2, which diffract to 2.2,Å, and cubic crystals of space group P4232, which diffract to 3.4,Å. [source]

Purification, crystallization and preliminary crystallographic studies on 2-dehydro-3-deoxygalactarate aldolase from Leptospira interrogans

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 12 2006
Xu Li
2-Dehydro-3-deoxygalactarate (DDG) aldolase is a member of the class II aldolase family and plays an important role in the pyruvate-metabolism pathway, catalyzing the reversible aldol cleavage of DDG to pyruvate and tartronic semialdehyde. As it is a potential novel antibiotic target, it is necessary to elucidate the catalytic mechanism of DDG aldolase. To determine the crystal structure, crystals of DDG aldolase from Leptospira interrogans were obtained by the hanging-drop vapour-diffusion method. The crystals diffracted to 2.2,Å resolution using a Cu,K, rotating-anode X-ray source. The crystal belonged to space group C2, with unit-cell parameters a = 293.5, b = 125.6, c = 87.6,Å, , = 100.9°. The VM is calculated to be 2.4,Å3,Da,1, assuming there to be 12 protein molecules in the asymmetric unit. [source]

Structure of macrophomate synthase

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 7 2004
Toyoyuki Ose
Macrophomate synthase (MPS) is an enzyme that catalyzes an extraordinarily complex conversion reaction, including two decarboxylations, two carbon,carbon bond formations and a dehydration, to form the benzoate analogue macrophomate from a 2-pyrone derivative and oxalacetate. Of these reactions, the two carbon,carbon bond formations are especially noteworthy because previous experiments have indicated that they proceed via a Diels,Alder reaction, one of the most widely used reactions in organic synthesis. The structural evidence that MPS catalyzes an intermolecular Diels,Alder reaction has been reported recently [Ose et al. (2003), Nature (London), 422, 185,189]. Interestingly, the tertiary structure as well as the quaternary structure of MPS are similar to those of 2-dehydro-3-deoxygalactarate (DDG) aldolase, a carbon,carbon bond-forming enzyme that catalyzes the reversible reaction of aldol condensation/cleavage. Here, the structure of MPS is described in detail and compared with that of DDG aldolase. Both enzymes have a (,/,)8 -barrel fold and are classified as belonging to the enolase superfamily based on their reaction strategy. The basic principles for carbon,carbon bond formation used by both MPS and DDG aldolase are the same with regard to trapping the enolate substrate and inducing subsequent reaction. The major differences in the active sites between these two enzymes are the recognition mechanisms of the second substrates, 2-pyrone and DDG, respectively. [source]