Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:6.4.1.2 (acetyl-CoA carboxylase)
2,876 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The unresolved autotrophic CO2 fixation pathways in the sulfur-reducing Archaebacterium Thermoproteus neutrophilus and in the phototrophic Eubacterium Chloroflexus aurantiacus have been investigated. Autotrophically growing cultures were labelled with [1,4-13C1]succinate, and the 13C pattern in cell constituents was determined by 1H- and 13C-NMR spectroscopy of purified amino acids and other cell constituents. In both organisms succinate contributed to less than 10% of cell carbon, the major part of carbon originated from CO2. All cell constituents became 13C-labelled, but different patterns were observed in the two organisms. This proves that two different cyclic CO2 fixation pathways are operating in autotrophic carbon assimilation in both of which succinate is an intermediate. The 13C-labelling pattern in T. neutrophilus is consistent with the operation of a reductive citric acid cycle and rules out any other known autotrophic CO2 fixation pathway. Surprisingly, the proffered [1,4-13C1]succinate was partially converted to double-labelled [3,4-13C2]glutamate, but not to double-labelled aspartate. These findings suggest that the conversion of citrate to 2-oxoglutarate is readily reversible under the growth conditions used, and a reversible citrate cleavage reaction is proposed. The 13C-labelling pattern in C. aurantiacus disagrees with any of the established CO2 fixation pathways; it therefore demands a novel autotrophic CO2 fixation cycle in which 3-hydroxypropionate and succinate are likely intermediates. The bacterium excreted substantial amounts of 3-hydroxypropionate (5 mM) and succinate (0.5 mM) at the end of autotrophic growth. Autotrophically grown Chloroflexus cells contained acetyl-CoA carboxylase and propionyl-CoA carboxylase activity. These enzymes are proposed to be the main CO2-fixing enzymes resulting in malonyl-CoA and methylmalonyl-CoA formation; from these carboxylation products 3-hydroxypropionate and succinate, respectively, can be formed.
...
PMID:13C-NMR study of autotrophic CO2 fixation pathways in the sulfur-reducing Archaebacterium Thermoproteus neutrophilus and in the phototrophic Eubacterium Chloroflexus aurantiacus. 157 76

The fatty acids which are common to and characteristic of shellfish, were identified by mass spectrometry and NMR spectral analyses as being: octadecatetraenoioc acid, eicosapentaenoic acid, docosapentaenoic acid and docosahexaenoic acid. When the fatty acids isolated by high performance liquid chromatography were separately intubated into rats, hepatic glucose-6-phosphate dehydrogenase (EC 1.1.1.49), malic enzyme (EC 1.1.1.40) and acetyl-CoA carboxylase (EC 6.4.1.2) were reduced more effectively as compared with linoleic acid intubation. These enzymes were reduced most markedly by eicosapentaenoic acid-intubation. The fatty acids seem to be effective components in reduction of triacylglycerol and lipogenic enzyme levels in rats fed on shellfish.
...
PMID:Identification of shellfish fatty acids and their effects on lipogenic enzymes. 610 86

A biotinylated acetyl-CoA carboxylase from the microaerophilic bacterium Helicobacter pylori was partially purified and characterized. The approximate molecular mass of the native enzyme was estimated at 235 kDa by native PAGE. A single band corresponding to approximately 24 kDa was detected by SDS-PAGE, suggesting that the native enzyme is a multi-protein complex. The protein was isolated from the soluble fraction of the cell. Catalytic activity was acetyl-CoA-dependent and inhibited by avidin but unaffected by avidin pretreated with excess biotin. The end-product of the reaction was identified as malonyl-CoA and the reaction was shown to be reversible by NMR spectroscopy. The activity of the enzyme was 0.29 mumol min-1 (mg protein)-1. The Vmax for bicarbonate was calculated at 0.73 mumol min-1 (mg protein)-1, and the affinity of the enzyme for this substrate was relatively low, with an apparent Km of 16.6 mM. These data provide the first evidence of a possible physiological role for the requirement of high levels of CO2 for growth in vitro of this bacterium.
...
PMID:Acetyl-CoA carboxylase activity in Helicobacter pylori and the requirement of increased CO2 for growth. 857 4

Transcarboxylase (TC) is a biotin-containing enzyme catalyzing the transfer of a carboxyl group from methylmalonyl-CoA to pyruvate to form propionyl-CoA and oxalacetate. The transfer is achieved via carboxylated biotin bound to a 1.3S subunit within the multisubunit enzyme complex. The 1.3S subunit of TC is a 123 amino acid polypeptide, to which biotin is covalently attached at Lys 89. We have overexpressed 1.3S in Escherichia coli and characterized the biotinylated and apo-forms by 1D- and 2D-NMR spectroscopy. To search for protein-biotin interactions, which could modulate the reactivity of the biotin ring on the 1.3S subunit, we have compared the chemical shifts, relaxation parameters, and NH exchange rates of the ureido ring protons of free and 1.3S-bound biotin. These properties are similar for both forms of the biotin. Further, NOE experiments on 1.3S revealed no detectable cross peaks between biotin and the protein. Consistent with these findings, the 2D NMR data for holo- and apo-1.3S are essentially identical indicating little or no changes in conformation between the two forms of the protein. The conclusion that strong protein-biotin interactions do not exist in 1.3S contrasts with the findings for the biotin carboxylase carrier protein from E. coli acetyl-CoA carboxylase, which reveal significant biotin-protein contacts [Athappilly, F. K., and Hendrickson, W. A. (1995) Structure 3, 1407-1419]. Further, the biotin NH1' exchange rates determined for 1.3S show that in the region of optimal activity for TC (pH 5.5-6.5) acid-catalyzed exchange predominates. In this pH range the base-catalyzed rate is too small (< 1 s-1) to account for the turnover rate of the enzyme. Thus, the means by which the N1' atom is activated for nucleophilic attack of the carboxyl group in methylmalonyl-CoA does not appear to depend on interactions within the 1.3S subunit alone; rather activation must occur at the interfaces of the subunits in the holoenzyme.
...
PMID:Absence of observable biotin-protein interactions in the 1.3S subunit of transcarboxylase: an NMR study. 939 86

The biotin carboxyl carrier protein (BCCP) is a subunit of acetyl-CoA carboxylase, a biotin-dependent enzyme that catalyzes the first committed step of fatty acid biosynthesis. In its functional cycle the biotin carboxyl carrier protein engages in heterologous protein-protein interactions with three distinct partners, depending on its state of posttranslational modification. Apo-BCCP interacts specifically with the biotin holoenzyme synthetase, BirA, which results in the posttranslational attachment of biotin to an essential lysine residue on BCCP. Holo-BCCP then interacts with the biotin carboxylase subunit, which leads to the addition of the carboxylate group of bicarbonate to biotin. Finally, the carboxybiotinylated form of BCCP interacts with transcarboxylase in the conversion of acetyl-CoA to malonyl-CoA. The determinants of protein-protein interaction specificity in this system are unknown. One hypothesis is that posttranslational modification of BCCP may result in conformational changes that regulate specific protein-protein interactions. To test this hypothesis, we have determined the NMR solution structure of the unbiotinylated form of an 87 residue C-terminal domain fragment of BCCP (apoBCCP87) from Escherichia coli acetyl-CoA carboxylase and compared this structure with the high-resolution structure of the biotinylated form that was recently solved by X-ray crystallographic techniques. Although the overall folding of the two proteins is highly similar, small structural differences are apparent for residues of the biotin-binding loop that may be important for mediating specific protein-protein interactions.
...
PMID:Structure of the carboxy-terminal fragment of the apo-biotin carboxyl carrier subunit of Escherichia coli acetyl-CoA carboxylase. 939 36

The recent discovery of leptin receptors in peripheral tissue raises questions about which of leptin's biological actions arise from direct effects of the hormone on extraneural tissues and what intracellular mechanisms are responsible for leptin's effects on carbohydrate and lipid metabolism. The present study is focused on the action of leptin on hepatic metabolism. Nondestructive 13C NMR methodology was used to follow the kinetics of intermediary metabolism by monitoring flux of 13C-labeled substrate through several multistep pathways. In perfused liver from either ob/ob or lean mice, we found that acute treatment with leptin in vitro modulates pathways controlling carbohydrate flux into 13C-labeled glycogen, thereby rapidly enhancing synthesis by an insulin-independent mechanism. Acute treatment of ob/ob liver also caused a rapid stimulation of long-chain fatty acid synthesis from 13C-labeled acetyl-CoA by the de novo synthesis route. Chronic leptin treatment in vivo induced homeostatic changes that resulted in a tripling of the rate of glycogen synthesis via the gluconeogenic pathway from [2-13C]pyruvate in ob/ob mouse liver perfused in the absence of the hormone. Consistent with the 13C NMR results, leptin treatment of the ob/ob mouse in vivo resulted in significantly increased hepatic glycogen synthase activity. Chronic treatment with leptin in vivo exerted the opposite effect of acute treatment in vitro and markedly decreased hepatic de novo synthesis of fatty acids in ob/ob mouse liver. In agreement with the 13C NMR findings, activities of hepatic acetyl-CoA carboxylase and fatty acid synthase were significantly reduced by chronic treatment of the ob/ob mouse with leptin. Our data represent a demonstration of direct effects of leptin in the regulation of metabolism in the intact functioning liver.
...
PMID:13C NMR study of the effects of leptin treatment on kinetics of hepatic intermediary metabolism. 963 58

The biotin carboxyl carrier protein (BCCP) is a subunit of acetyl-CoA carboxylase, a biotin-dependent enzyme that catalyzes the first committed step of fatty acid biosynthesis. In its functional cycle, this protein engages in heterologous protein-protein interactions with three distinct partners, depending on its state of post-translational modification. Apo-BCCP interacts specifically with the biotin holoenzyme synthetase, BirA, which results in the post-translational attachment of biotin to a single lysine residue on BCCP. Holo-BCCP then interacts with the biotin carboxylase subunit of acetyl-CoA carboxylase, which leads to the addition of the carboxylate group of bicarbonate to biotin. Finally, the carboxy-biotinylated form of BCCP interacts with transcarboxylase in the transfer of the carboxylate to acetyl-CoA to form malonyl-CoA. The determinants of protein-protein interaction specificity in this system are unknown. The NMR solution structure of the unbiotinylated form of an 87 residue C-terminal domain fragment (residue 70-156) of BCCP (holoBCCP87) and the crystal structure of the biotinylated form of a C-terminal fragment (residue 77-156) of BCCP from Escherichia coli acetyl-CoA carboxylase have previously been determined. Comparative analysis of these structures provided evidence for small, localized conformational changes in the biotin-binding region upon biotinylation of the protein. These structural changes may be important for regulating specific protein-protein interactions. Since the dynamic properties of proteins are correlated with local structural environments, we have determined the relaxation parameters of the backbone 15N nuclear spins of holoBCCP87, and compared these with the data obtained for the apo protein. The results indicate that upon biotinylation, the inherent mobility of the biotin-binding region and the protruding thumb, with which the biotin group interacts in the holo protein, are significantly reduced.
...
PMID:Comparison of the backbone dynamics of the apo- and holo-carboxy-terminal domain of the biotin carboxyl carrier subunit of Escherichia coli acetyl-CoA carboxylase. 1004 24

Transcarboxylase (TC) from Propionibacterium shermanii, a biotin-dependent enzyme, catalyzes the transfer of a carboxyl group from methylmalonyl-CoA to pyruvate to form propionyl-CoA and oxalacetate. Within the multi-subunit enzyme complex, the 1.3S subunit functions as the carboxyl group carrier and also binds the other two subunits to assist in the overall assembly of the enzyme. The 1.3S subunit is a 123 amino acid polypeptide (12.6 kDa) to which biotin is covalently attached at Lys 89. The three-dimensional solution structure of the full-length holo-1.3S subunit of TC has been solved by multidimensional heteronuclear NMR spectroscopy. The C-terminal half of the protein (51-123) is folded into a compact all-beta-domain comprising of two four-stranded antiparallel beta-sheets connected by short loops and turns. The fold exhibits a high 2-fold internal symmetry and is similar to that of the biotin carboxyl carrier protein (BCCP) of acetyl-CoA carboxylase, but lacks an extension that has been termed "protruding thumb" in BCCP. The first 50 residues, which have been shown to be involved in intersubunit interactions in the intact enzyme, appear to be disordered in the isolated 1.3S subunit. The molecular surface of the folded domain has two distinct surfaces: one side is highly charged, while the other comprises mainly hydrophobic, highly conserved residues.
...
PMID:High resolution solution structure of the 1.3S subunit of transcarboxylase from Propionibacterium shermanii. 1070

The lipoyl domains of 2-oxo acid dehydrogenase multienzyme complexes and the biotinyl domains of biotin-dependent enzymes have homologous structures, but the target lysine residue in each domain is correctly selected for posttranslational modification by lipoyl protein ligase and biotinyl protein ligase, respectively. We have applied two-dimensional heteronuclear NMR spectroscopy to investigate the interaction between the apo form of the biotinyl domain of the biotin carboxyl carrier protein of acetyl-CoA carboxylase and the biotinyl protein ligase (BPL) from Escherichia coli. Heteronuclear multiple quantum coherence NMR spectra of the 15N-labelled biotinyl domain were recorded in the presence and absence of the ligase and backbone amide 1H and 15N chemical shifts were evaluated. Small, but significant, changes in chemical shift were found in two regions, including the tight beta-turn that houses the lysine residue targetted for biotinylation, and the beta-strand 2 and the loop that precedes it in the domain. When compared with the three-dimensional structure, sequence alignments of other biotinyl and lipoyl domains, and mutagenesis data, these results give a clear indication of how the biotinyl domain is both recognised by BPL and distinguished from the structurally related lipoyl domain to ensure correct posttranslational modification.
...
PMID:Heteronuclear NMR studies of the specificity of the post-translational modification of biotinyl domains by biotinyl protein ligase. 1098 14

Biotin carboxyl carrier protein (BCCP) is the small biotinylated subunit of Escherichia coli acetyl-CoA carboxylase (ACC), the enzyme that catalyzes the first committed step of fatty acid synthesis. Similar proteins are found in other bacteria and in chloroplasts. E. coli BCCP is a member of a large family of protein domains modified by covalent attachment of biotin to a specific lysine residue. However, the BCCP biotinyl domain differs from many of these proteins in that an eight-amino acid residue insertion is present upstream of the biotinylated lysine. X-ray crystallographic and multidimensional NMR studies show that these residues constitute a structure that has the appearance of an extended thumb that protrudes from the otherwise highly symmetrical domain structure. I report that expression of two mutant BCCPs lacking the thumb residues fails to restore growth and fatty acid synthesis to a temperature-sensitive E. coli strain that lacks BCCP when grown at nonpermissive temperature. Alignment of BCCPs from various organisms shows that only two of the eight thumb residues are strictly conserved, and amino acid substitution of either residue results in proteins giving only weak growth of the temperature-sensitive E. coli strain. Therefore, the thumb structure is essential for the function of BCCP in the ACC reaction and provides a useful motif for distinguishing the biotinylated proteins of multisubunit ACCs from those of enzymes catalyzing other biotin-dependent reactions. An unexpected result was that expression of a mutant BCCP in which the biotinylated lysine residue was substituted with cysteine was able to partially restore growth and fatty acid synthesis to the temperature-sensitive E. coli strain. This complementation was shown to be specific to BCCPs having native structure (excepting the biotinylated lysine) and is interpreted in terms of dimerization of the BCCP biotinyl domain during the ACC reaction.
...
PMID:The biotinyl domain of Escherichia coli acetyl-CoA carboxylase. Evidence that the "thumb" structure id essential and that the domain functions as a dimer. 1149 22


1 2 Next >>

---