Search results for "Thioester"

Chemical Proteomic Analysis of Serine Hydrolase Activity in Niemann-Pick Type C Mouse Brain

2018

The endocannabinoid system (ECS) is considered to be an endogenous protective system in various neurodegenerative diseases. Niemann-Pick type C (NPC) is a neurodegenerative disease in which the role of the ECS has not been studied yet. Most of the endocannabinoid enzymes are serine hydrolases, which can be studied using activity-based protein profiling (ABPP). Here, we report the serine hydrolase activity in brain proteomes of a NPC mouse model as measured by ABPP. Two ABPP methods are used: a gel-based method and a chemical proteomics method. The activities of the following endocannabinoid enzymes were quantified: diacylglycerol lipase (DAGL) α, α/β-hydrolase domain-containing protein 4, α…

Pot-Economy Autooxidative Condensation of 2-Aryl-2-lithio-1,3-dithianes

2018

The autoxidative condensation of 2-aryl-2-lithio-1,3-dithianes is here reported. Treatment of 2-aryl-1,3-dithianes with n-BuLi in the absence of any electrophile leads to condensation of three molecules of 1,3-dithianes and formation of highly functionalized α-thioether ketones orthothioesters in 51-89% yields upon air exposure. The method was further expanded to benzaldehyde dithioacetals, affording corresponding orthothioesters and α-thioether ketones in 48-97% yields. The experimental results combined with density functional theory studies support a mechanism triggered by the autoxidation of 2-aryl-2-lithio-1,3-dithianes to yield a highly reactive thioester that undergoes condensation wi…

Current state of clinical and morphological features in human NCL.

2004

The neuronal ceroid lipofuscinoses (NCL) are large group of autosomal recessive lysosomal storage disorders with both enzymatic deficiency and structural protein dysfunction. Previously, diagnosis of (NCL) was based on age at onset clinicopathological (C‐P) findings described 4 forms, classified as infantile (INCL) (2), late‐infantile (LINCL) (5), juvenile (JNCL) (6), and adult (ANCL) most patients with NCL have progressive ocular and cerebral dysfunvtion, including cognitive/motor dysfunction and uncontrolled seizures. After reviewing 520 patients with NCL, we found that about 104 (20%) did not fit this classification of NCL With further research, 4 additional forms have been recognized: F…

Structures of yeast peroxisomal Δ(3),Δ(2)-enoyl-CoA isomerase complexed with acyl-CoA substrate analogues: the importance of hydrogen-bond networks f…

2015

Δ3,Δ2-Enoyl-CoA isomerases (ECIs) catalyze the shift of a double bond from 3Z- or 3E-enoyl-CoA to 2E-enoyl-CoA. ECIs are members of the crotonase superfamily. The crotonase framework is used by many enzymes to catalyze a wide range of reactions on acyl-CoA thioesters. The thioester O atom is bound in a conserved oxyanion hole. Here, the mode of binding of acyl-CoA substrate analogues to peroxisomalSaccharomyces cerevisiaeECI (ScECI2) is described. The best defined part of the bound acyl-CoA molecules is the 3′,5′-diphosphate-adenosine moiety, which interacts with residues of loop 1 and loop 2, whereas the pantetheine part is the least well defined. The catalytic base, Glu158, is hydrogen-bo…

Combinatorial Biosynthesis of Polyketides

2003

Selective isomerization of a trans -butanediacetal derivative of tartaric acid with differentiating substituents at C-2 and C-3

2017

Abstract A trans-disubstituted butanediacetal derivative with two different substituents (ester and thioester) – methyl (2R,3R,5R,6R)-3-ethylsulfanylcarbonyl-5,6-dimethoxy-5,6-dimethyl-1,4-dioxane-2-carboxylate, was selectively converted to the cis derivative – methyl (2S,3R,5R,6R)-3-ethylsulfanylcarbonyl-5,6-dimethoxy-5,6-dimethyl-1,4-dioxane-2-carboxylate in high yield on a multigram scale. The product of this reaction offers the possibility for selective modification of one of the substituents, which was demonstrated by Fukuyama reduction of the thioester group.

The Catalytic Mechanism of Carboxylesterases: A Computational Study

2014

The catalytic mechanism of carboxylesterases (CEs, EC 3.1.1.1) is explored by computational means. CEs hydrolyze ester, amide, and carbamate bonds found in xenobiotics and endobiotics. They can also perform transesterification, a reaction important, for instance, in cholesterol homeostasis. The catalytic mechanisms with three different substrates (ester, thioester, and amide) have been established at the M06-2X/6-311++G**//B3LYP/6-31G* level of theory. It was found that the reactions proceed through a mechanism involving four steps instead of two as is generally proposed: (i) nucleophilic attack of serine to the substrate, forming the first tetrahedral intermediate, (ii) formation of the ac…

Thioester-functionalised and oxime-based hexametallic manganese(iii) single-molecule magnets

2017

Two novel hexametallic MnIII complexes of formulae [Mn6(μ3-O)2(H2N-sao)6(3-atpa)2(EtOH)6]·2EtOH·2H2O (1) and [Mn6(μ3-O)2(H2N-sao)6(6-atha)2(EtOH)6]·6EtOH (2) [H2N-saoH2 = salicylamidoxime, 3-hatpa = 3-(acetylthio)propionic acid, 6-hatha = 6-(acetylthio)hexanoic acid] have been synthesised by using thioester-carboxylate ligands and magnetostructurally characterised. 1 crystallises in the triclinic system with space group P and 2 crystallises in the monoclinic system with space group P21/c. The study of the dc and ac magnetic susceptibility reveals single-molecule magnet behaviour for both compounds with spin-ground states S = 12 and S = 4 for 1 and 2, respectively. Hence, 1 and 2 are new mem…

Stereoselective reactions of a thioester butanediacetal with various electrophiles

2014

Abstract The reactions of the lithium enolate of S -ethyl (2 R ,5 R ,6 R )-5,6-dimethoxy-5,6-dimethyl-[1,4]-dioxane-2-carbothioate were investigated in the presence or absence of hexamethylphosphoramide (HMPA). Fluorination gave a single isomer with a much better yield than for the corresponding methyl ester. Alkylation with alkyl halides strongly depended upon their structure. Without HMPA, only methyl iodide reacted with moderate yield and gave a single isomer. In the presence of HMPA, all of the alkyl halides reacted almost quantitatively (81–98% yield) with moderate stereoselectivity and preferentially gave products with the alkyl chain attached at the equatorial position. The silyl eno…

Dementia in the Neuronal Ceroidlipofuscinoses

2001

Dementia is defined as a decline in cognitive abilities such as impairment of memory, reasoning, behaviour, attention, motivation and effectiveness. The term usually implies that normal mature mental capability was achieved before, and it is therefore mostly ascribed to adult patients.