Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:6.4.1.2 (acetyl-CoA carboxylase)
 2,876 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The acetyl-CoA carboxylase present in both wheat germ and total wheat leaf protein contains ca. 220 kDa subunits. It is the major biotin-dependent carboxylase present in wheat chloroplasts. Active acetyl-CoA carboxylase purified from wheat germ is a homodimer with an apparent molecular mass of ca. 500 kDa. The enzyme from wheat germ or from wheat chloroplasts is sensitive to the herbicide haloxyfop at micromolar levels. The incorporation of 14C-acetate into fatty acids in freshly cut wheat seedling leaves provides a convenient in vivo assay for both acetyl-CoA carboxylase and haloxyfop.
 ...
PMID:Wheat acetyl-CoA carboxylase. 810 Nov 4

The 280-kDa beta-isoform of acetyl-CoA carboxylase (ACCbeta) is predominantly expressed in heart and skeletal muscle, whereas the 265-kDa alpha-isoform (ACCalpha) is the major ACC in lipogenic tissues. The ACCbeta promoter showed myoblast-specific promoter activity and was strongly induced by MyoD in NIH3T3 cells. Serial deletions of the promoter revealed that MyoD acts on the E-boxes located at positions -498 to -403 and on the proximal region including the 5'-untranslated region. Destruction of the E-boxes at positions -498 to -403 by site-directed mutagenesis resulted in a significant decrease of MyoD responsiveness. The "TGAAA" at -32 to -28 and the region around the transcription start site play important roles in basal transcription, probably as a TATA box and an Inr element, respectively. Mutations of another E-box at -14 to -9 and a "GCCTGTCA" sequence at +17 to +24 drastically decreased the MyoD responsiveness. The novel cis-element GCCTGTCA was preferentially bound by MyoD homodimer in EMSA and conferred MyoD responsiveness to a luciferase reporter, which was repressed by the overexpression of E12. This finding is unique since activation via E-boxes is mediated by heterodimers of MyoD and E-proteins. We screened a human skeletal muscle cDNA library to isolate clones expressing proteins that bind to the region around the GCCTGTCA (+8 to +27) sequence, and isolated Myf4 and Myf6 cDNAs. Electrophoretic mobility shift assay showed that recombinant Myf4 and Myf6 bind to this novel cis-element. Moreover, transient expression of Myf6 induced significant activation on the ACCbeta promoter or an artificial promoter harboring this novel cis-element. These findings suggest that muscle regulatory factors, such as MyoD, Myf4, and Myf6, contribute to the muscle-specific expression of ACCbeta via E-boxes and the novel cis-element GCCTGTCA.
 ...
PMID:Cloning of human acetyl-CoA carboxylase beta promoter and its regulation by muscle regulatory factors. 1107 40

Biotin carboxylase catalyzes the ATP-dependent carboxylation of biotin and is one component of the multienzyme complex acetyl-CoA carboxylase that catalyzes the first committed step in fatty acid synthesis. The Escherichia coli biotin carboxylase is readily isolated from the other components of the acetyl-CoA carboxylase complex such that enzymatic activity is retained. The three-dimensional structure of biotin carboxylase, determined by x-ray crystallography, demonstrated that the enzyme is a homodimer consisting of two active sites in which each subunit contains a complete active site. To understand how each subunit contributes to the overall function of biotin carboxylase, we made hybrid molecules in which one subunit had a wild-type active site, and the other subunit contained an active site mutation known to significantly affect the activity of the enzyme. One of the two genes encoded a poly-histidine tag at its N terminus, whereas the other gene had an N-terminal FLAG epitope tag. The two genes were assembled into a mini-operon that was induced to give high level expression of both enzymes. "Hybrid" dimers composed of one subunit with a wild-type active site and a second subunit having a mutant active site were obtained by sequential chromatographic steps on columns of immobilized nickel chelate and anti-FLAG affinity matrices. In vitro kinetic studies of biotin carboxylase dimers in which both subunits were wild type revealed that the presence of the N-terminal tags did not alter the activity of the enzyme. However, kinetic assays of hybrid dimer biotin carboxylase molecules in which one subunit had an active site mutation (R292A, N290A, K238Q, or E288K) and the other subunit had a wild-type active site resulted in 39-, 28-, 94-, and 285-fold decreases in the activity of these enzymes, respectively. The dominant negative effects of these mutant subunits were also detected in vivo by monitoring the rate of fatty acid biosynthesis by [(14)C]acetate labeling of cellular lipids. Expression of the mutant biotin carboxylase genes from an inducible arabinose promoter resulted in a significantly reduced rate of fatty acid synthesis relative to the same strain that expressed the wild type gene. Thus, both the in vitro and in vivo data indicate that both subunits of biotin carboxylase are required for activity and that the two subunits must be in communication during enzyme function.
 ...
PMID:Function of Escherichia coli biotin carboxylase requires catalytic activity of both subunits of the homodimer. 1139 Apr 6

Biotin protein ligase (EC 6.3.4.15) catalyses the synthesis of an activated form of biotin, biotinyl-5'-AMP, from substrates biotin and ATP followed by biotinylation of the biotin carboxyl carrier protein subunit of acetyl-CoA carboxylase. The three-dimensional structure of biotin protein ligase from Pyrococcus horikoshii OT3 has been determined by X-ray diffraction at 1.6A resolution. The structure reveals a homodimer as the functional unit. Each subunit contains two domains, a larger N-terminal catalytic domain and a smaller C-terminal domain. The structural feature of the active site has been studied by determination of the crystal structures of complexes of the enzyme with biotin, ADP and the reaction intermediate biotinyl-5'-AMP at atomic resolution. This is the first report of the liganded structures of biotin protein ligase with nucleotide and biotinyl-5'-AMP. The structures of the unliganded and the liganded forms are isomorphous except for an ordering of the active site loop upon ligand binding. Catalytic binding sites are suitably arranged to minimize the conformational changes required during the reaction, as the pockets for biotin and nucleotide are located spatially adjacent to each other in a cleft of the catalytic domain and the pocket for biotinyl-5'-AMP binding mimics the combination of those of the substrates. The exact locations of the ligands and the active site residues allow us to propose a general scheme for the first step of the reaction carried out by biotin protein ligase in which the positively charged epsilon-amino group of Lys111 facilitates the nucleophilic attack on the ATP alpha-phosphate group by the biotin carboxyl oxygen atom and stabilizes the negatively charged intermediates.
 ...
PMID:Crystal structures of biotin protein ligase from Pyrococcus horikoshii OT3 and its complexes: structural basis of biotin activation. 1616 57

Biotin-protein ligase is an enzyme that catalyzes the ATP-dependent biotinylation of a specific lysine residue in acetyl-CoA carboxylase. The biotin-protein ligase from Pyrococcus horikoshii OT3 has been cloned, overexpressed and purified. Crystallization was performed by the microbatch method or the vapour-diffusion method using PEG 2000 as a precipitant at 295 K. X-ray diffraction data have been collected to 1.6 A resolution from a native crystal and to 1.55 A resolution from a selenomethionine-derivative crystal for multiple anomalous dispersion phasing using synchrotron radiation at 100 K. The native crystal belongs to the monoclinic space group P2(1), with unit-cell parameters a = 38.601, b = 78.264, c = 70.147 A, beta = 101.48 degrees. Assuming a homodimer per asymmetric unit gives a VM value of 2.14 A3 Da(-1) and a solvent content of 42.5%. Cocrystals with biotin, ADP and biotinyl-5'-AMP were prepared and diffraction data sets were collected to 1.6, 1.6 and 1.45 A resolution, respectively.
 ...
PMID:Purification, crystallization and preliminary crystallographic analysis of the biotin-protein ligase from Pyrococcus horikoshii OT3. 1651 Sep 91

Biotin carboxylase catalyzes the ATP-dependent carboxylation of biotin and is one component of the multienzyme complex acetyl-CoA carboxylase that catalyzes the first committed step in fatty acid synthesis in all organisms. In Escherichia coli, biotin carboxylase exists as a homodimer where each subunit contains a complete active site. In a previous study (Janiyani, K., Bordelon, T., Waldrop, G.L., Cronan Jr., J.E., 2001. J. Biol. Chem. 276, 29864-29870), hybrid dimers were constructed where one subunit was wild-type and the other contained an active site mutation that reduced activity at least 100-fold. The activity of the hybrid dimers was only slightly greater than the activity of the mutant homodimers and far less than the expected 50% activity for completely independent active sites. Thus, there is communication between the two subunits of biotin carboxylase. The dominant negative effect of the mutations on the wild-type active site was interpreted as alternating catalytic cycles of the active sites in the homodimer. In order to test the hypothesis of oscillating catalytic cycles, mathematical modeling and numerical simulations of the kinetics of wild-type, hybrid dimers, and mutant homodimers of biotin carboxylase were performed. Numerical simulations of biotin carboxylase kinetics were the most similar to the experimental data when an oscillating active site model was used. In contrast, alternative models where the active sites were independent did not agree with the experimental data. Thus, the numerical simulations of the proposed kinetic model support the hypothesis that the two active sites of biotin carboxylase alternate their catalytic cycles.
 ...
PMID:Modeling and numerical simulation of biotin carboxylase kinetics: implications for half-sites reactivity. 1726 90

Bacterial acetyl-CoA carboxylase is a multifunctional biotin-dependent enzyme that consists of three separate proteins: biotin carboxylase (BC), biotin carboxyl carrier protein (BCCP), and carboxyltransferase (CT). Acetyl-CoA carboxylase is a potentially attractive target for novel antibiotics because it catalyzes the first committed step in fatty acid biosynthesis. In the first half-reaction, BC catalyzes the ATP-dependent carboxylation of BCCP. In the second half-reaction, the carboxyl group is transferred from carboxybiotinylated BCCP to acetyl-CoA to produce malonyl-CoA. A series of structures of BC from several bacteria crystallized in the presence of various ATP analogs is described that addresses three major questions concerning the catalytic mechanism. The structure of BC bound to AMPPNP and the two catalytically essential magnesium ions resolves inconsistencies between the kinetics of active-site BC mutants and previously reported BC structures. Another structure of AMPPNP bound to BC shows the polyphosphate chain folded back on itself, and not in the correct (i.e., extended) conformation for catalysis. This provides the first structural evidence for the hypothesis of substrate-induced synergism, which posits that ATP binds nonproductively to BC in the absence of biotin. The BC homodimer has been proposed to exhibit half-sites reactivity where the active sites alternate or "flip-flop" their catalytic cycles. A crystal structure of BC showed the ATP analog AMPPCF(2)P bound to one subunit while the other subunit was unliganded. The liganded subunit was in the closed or catalytic conformation while the unliganded subunit was in the open conformation. This provides the first structural evidence for half-sites reactivity in BC.
 ...
PMID:Structural evidence for substrate-induced synergism and half-sites reactivity in biotin carboxylase. 1872 55

The ability of a single protein to interact with multiple protein partners is central to many biological processes. However, the physical-chemical and structural basis of the multispecificity is not understood. In Escherichia coli, the protein BirA can self-associate to a homodimer or form a heterodimer with the biotin carboxyl carrier protein of the biotin-dependent carboxylase, acetyl coenzyme A carboxylase. The first interaction results in binding of BirA to the biotin operator sequence to repress transcription initiation at the biotin biosynthetic operon and the second is a prerequisite to posttranslational biotin addition to the carrier protein for use in metabolism. A single surface on BirA is used for both interactions and previous studies indicate that, despite the structural differences between the alternative partners, the two dimerization reactions are isoenergetic. In this work, the underlying thermodynamic driving forces and the sequence determinants of the two interactions were investigated in order to elucidate the energetic and structural underpinnings of the dual specificity. Combined measurements of the temperature and salt dependencies of heterodimerization indicate a modest unfavorable enthalpy and no dependence on salt concentration. By contrast, homodimerization is characterized by a very large unfavorable enthalpy and a modest dependence on salt concentration. Measurements of the function of BirA variants with single amino acid replacements in the alternative dimerization reactions indicate that although considerable overlap in structural determinants for both interactions exists, hotspots specific for one but not the other were detected.
 ...
PMID:Thermodynamic and structural investigation of bispecificity in protein-protein interactions. 1936 26

It is known that a high-cholesterol diet induces oxidative stress, inflammatory response, and beta-amyloid (Abeta) accumulation in mouse brain, resulting in neurodegenerative changes. Quercetin, a naturally occurring flavonoid, has been reported to possess numerous biological activities beneficial to health. Our previous studies have demonstrated that quercetin protects mouse brain against D-galactose-induced oxidative damage. Against this background, we evaluated the effect of quercetin on high-cholesterol-induced neurotoxicity in old mice and explored its potential mechanism. Our results showed that oral administration of quercetin significantly improved the behavioural performance of high-cholesterol-fed old mice in both a step-through test and the Morris water maze task. This is at least in part caused by decreasing ROS and protein carbonyl levels and restoring Cu--Zn superoxide dismutase (Cu, Zn-SOD) activity. Furthermore, quercetin also significantly activated the AMP-activated protein kinase (AMPK) via down-regulation of protein phosphatase 2C (PP2C), which reduced the integral optical density (IOD) of activated microglia cells and CD11b expression, down-regulated iNOS and cyclooxygenase-2 (COX-2) expression, and decreased IL-1beta, IL-6, and TNF-alpha expression in the brains of high-cholesterol-fed old mice through the suppression of NF-kappaB p65 nuclear translocation. Moreover, AMPK activation significantly increased 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase and acetyl-CoA carboxylase (ACC) phosphorylation and reduced fatty acid synthase (FAS) expression in the brains of high-cholesterol-fed old mice, which reduced cholesterol levels, down-regulated cholesterol 24-hydroxylase (CYP46A1) and beta-amyloid converting enzyme 1 (BACE1) expression, decreased eukaryotic translation initiation factor 2alpha (eIF2alpha) phosphorylation, and lowered Abeta deposits. However, the neuroprotective effect of quercetin was weakened by intraperitoneal injection of compound C, an AMPK inhibitor. These results suggest that AMPK activated by quercetin may be a potential target to enhance the resistance of neurons to age-related diseases.
 ...
PMID:Quercetin activates AMP-activated protein kinase by reducing PP2C expression protecting old mouse brain against high cholesterol-induced neurotoxicity. 2092 14

We previously reported the effects of the total flavonoids (TFs) from Rosa laevigata Michx fruit against carbon tetrachloride-induced liver damage, non-alcoholic fatty liver disease, and liver ischemia-reperfusion injury. However, there have been no papers reporting the role of R. laevigata TFs against lipopolysaccharide (LPS)-induced liver injury. In this paper, liver injury in mice was induced by LPS, and R. Laevigata extract was intragastrically administered to the mice for 7 days. Biochemical parameters in serum and liver tissue were examined, and pathological changes were observed by transmission electron microscopy, hematoxylin and eosin (H&E) and Oil Red O staining. The results showed that the TFs markedly reduced serum ALT (alanine transferase), AST (aspartate transaminase), TG (total triglyceride), and TC (total cholesterol) levels and relative liver weights and improved liver pathological changes. In addition, the TFs markedly decreased tissue MDA (malondialdehyde) level and increased the levels of SOD (superoxide dismutase) and GSH-Px (glutathione peroxidase). A mechanistic study showed that the TFs significantly increased the expression levels of Nrf2 (nuclear erythroid factor2-related factor 2), HO-1 (heme oxygenase-1), NQO1 (NAD(P)H dehydrogenase (quinone 1), GCLC (glutamate-cysteine ligase catalytic subunit), and GCLM (glutamate-cysteine ligase regulatory subunit) and decreased Keap1 (Kelch-like ECH-associated protein 1) level by activating FXR (farnesoid X receptor) against oxidative stress. Furthermore, the TFs markedly suppressed the nuclear translocation of NF-κB (nuclear factor-kappa B) and subsequently decreased the expression levels of IL (interleukin)-1β, IL-6, HMGB-1 (high -mobility group box 1), and COX-2 (cyclooxygenase-2) by activating FXR and FOXO3a (forkhead box O3) against inflammation. Besides, the TFs obviously reduced the expression levels of SREBP-1c (sterol regulatory element-binding proteins-1c), ACC1 (acetyl-CoA carboxylase-1), FASN (fatty acid synthase), and SCD1 (stearoyl-coenzyme A desaturase 1), and improved CPT1 (carnitine palmitoyltransferase 1) level by activating FXR to regulate lipid metabolism. Our results suggest that TFs exhibited protective effect against LPS-induced liver injury by altering FXR-mediated oxidative stress, inflammation, and lipid metabolism, and should be developed as an effective food and healthcare product for the therapy of liver injury in the future.
 ...
PMID:Protection by the Total Flavonoids from Rosa laevigata Michx Fruit against Lipopolysaccharide-Induced Liver Injury in Mice via Modulation of FXR Signaling. 2989 Jun 50


1 2 Next >>