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

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Query: EC:1.3.99.3 (acyl-CoA dehydrogenase)
1,425 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two novel rare mutations, MCAD approximately 842G-->C (R256T) and MCAD approximately 1166A-->G (K364R), have been investigated to assess how far the biochemical properties of the mutant proteins correlate with the clinical phenotype of medium chain acyl-CoA dehydrogenase (MCAD) deficiency. When the gene for K364R was overexpressed in Escherichia coli, the synthesized mutant protein only exhibited activity when the gene for chaperonin GroELS was co-overexpressed. Levels of activity correlated with the amounts of native MCAD protein visible in western blots. The R256T mutant, by contrast, displayed no activity either with or without chaperonin, but in this case a strong MCAD protein band was seen in the western blots throughout. The proteins were also purified, and the enzyme function and thermostability investigated. The K364R protein showed only moderate kinetic impairment, whereas the R256T protein was again totally inactive. Neither mutant showed marked depletion of FAD. The pure K364R protein was considerably less thermostable than wild-type MCAD. Western blots indicated that, although the R256T mutant protein is less thermostable than normal MCAD, it is much more stable than K364R. Though clinically asymptomatic thus far, both mutations have a severe impact on the biochemical phenotype of the protein. K364R, like several previously described MCAD mutant proteins, appears to be defective in folding. R256T, by contrast, is a well-folded protein that is nevertheless devoid of catalytic activity. How the mutations specifically affect the catalytic activity and the folding is further discussed.
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PMID:Two novel variants of human medium chain acyl-CoA dehydrogenase (MCAD). K364R, a folding mutation, and R256T, a catalytic-site mutation resulting in a well-folded but totally inactive protein. 1612 23

Multiple acyl-CoA dehydrogenase deficiency (MADD) or glutaric aciduria type II (GAII) is most often caused by mutations in the genes encoding the alpha- or beta-subunit of electron transfer flavoprotein (ETF) or electron transfer flavoprotein dehydrogenase (ETF-DH). Since not all patients have mutations in these genes, other as yet unidentified genes are predicted to be involved as well. Because all affected mitochondrial flavoproteins in MADD have FAD as a prosthetic group, the underlying defect in these patients may be due to a thus far undisclosed disturbance in the metabolism of FAD. Since a proper mitochondrial flavin balance is maintained by a mitochondrial FAD transporter, a defect of this transporter could also cause an MADD-like phenotype. In yeast, FAD is transported across the mitochondrial inner membrane by the FLX1 protein. An FLX1-mutated Saccharomyces cerevisiae strain exhibits a decreased activity of several mitochondrial flavoproteins. In the present study, we report the identification of the human mitochondrial FAD transporter. Based on sequence similarity to FLX1, we identified two human candidate genes (MFT and N111), which were cloned and characterized by functional expression in an FLX1-mutated yeast strain. Of the two candidate genes, only the previously described mitochondrial folate transporter (MFT) was able to functionally complement the FLX1 mutant. Candidates for mutations in the MFT gene are patients with a clinical suspicion of MADD but without any mutation in the alpha- or beta-subunit of ETF or ETF-DH.
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PMID:Identification of the human mitochondrial FAD transporter and its potential role in multiple acyl-CoA dehydrogenase deficiency. 1616 86

Mitochondrial medium-chain acyl-CoA dehydrogenase is a key enzyme for the beta-oxidation of fatty acids, which catalyzes the FAD-dependent oxidation of a variety of acyl-CoA substrates to the corresponding trans-2-enoyl-CoA thioesters. Oct-4-en-2-ynoyl-CoA was identified as a new irreversible inhibitor of acyl-CoA dehydrogenase, and kinetic parameters K(I) and k(inact) were determined to be 11 microM and 0.025 min(-1), respectively. Triple bond between C2 and C3 of the inhibitor was identified as the functional group responsible for enzyme inactivation, and Michael addition is proposed as the mechanism for this inactivation, which is a new pathway for inactivation of MCAD by inhibitors. The inhibitor may become a lead for further development for treating non-insulin-dependent diabetes mellitus.
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PMID:Inactivation of medium-chain acyl-CoA dehydrogenase by oct-4-en-2-ynoyl-CoA. 1629 16

Short-chain acyl-CoA dehydrogenase (hSCAD) catalyzes the first matrix step in the mitochondrial beta-oxidation cycle with optimal activity toward butyryl- and hexanoyl-CoA. Two common variants of this enzyme encoding G185S and R147W substitutions have been identified at an increased frequency compared to the general population in patients with a wide variety of clinical problems, but functional studies of the purified mutant enzymes have shown only modestly changed kinetic properties. Moreover, both amino acid residues are located quite far from the catalytic pocket and the essential FAD cofactor. To clarify the potential relationship of these variants to clinical disease, we have further investigated their thermodynamic properties using spectroscopic and electrochemical techniques. Purified R147W hSCAD exhibited almost identical physical and redox properties to wild-type but only half of the specific activity and substrate activation shifts observed in wild-type enzyme. In contrast, the G185S mutant proved to have impairments of both its kinetic and electron transfer properties. Spectroelectrochemical studies reveal that G185S binding to the substrate/product couple produces an enzyme potential shift of only +88 mV, which is not enough to make the reaction thermodynamically favorable. For wild-type hSCAD, this barrier is overcome by a negative shift in the substrate/product couple midpoint potential, but in G185S this activation was not observed. When G185S was substrate bound, the midpoint potential of the enzyme actually shifted more negative. These results provide valuable insight into the mechanistic basis for dysfunction of the common variant hSCADs and demonstrate that mutations, regardless of their position in the protein structure, can have a large impact on the redox properties of the enzyme.
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PMID:Biochemical and electrochemical characterization of two variant human short-chain acyl-CoA dehydrogenases. 1633 63

Nitroalkane oxidase (NAO) from Fusarium oxysporum catalyzes the oxidation of neutral nitroalkanes to the corresponding aldehydes or ketones with the production of H(2)O(2) and nitrite. The flavoenzyme is a new member of the acyl-CoA dehydrogenase (ACAD) family, but it does not react with acyl-CoA substrates. We present the 2.2 A resolution crystal structure of NAO trapped during the turnover of nitroethane as a covalent N5-FAD adduct (ES*). The homotetrameric structure of ES* was solved by MAD phasing with 52 Se-Met sites in an orthorhombic space group. The electron density for the N5-(2-nitrobutyl)-1,5-dihydro-FAD covalent intermediate is clearly resolved. The structure of ES was used to solve the crystal structure of oxidized NAO at 2.07 A resolution. The c axis for the trigonal space group of oxidized NAO is 485 A, and there are six subunits (1(1)/(2) holoenzymes) in the asymmetric unit. Four of the active sites contain spermine (EI), a weak competitive inhibitor, and two do not contain spermine (E(ox)). The active-site structures of E(ox), EI, and ES* reveal a hydrophobic channel that extends from the exterior of the protein and terminates at Asp402 and the N5 position on the re face of the FAD. Thus, Asp402 is in the correct position to serve as the active-site base, where it is proposed to abstract the alpha proton from neutral nitroalkane substrates. The structures for NAO and various members of the ACAD family overlay with root-mean-square deviations between 1.7 and 3.1 A. The homologous region typically spans more than 325 residues and includes Glu376, which is the active-site base in the prototypical member of the ACAD family. However, NAO and the ACADs exhibit differences in hydrogen-bonding patterns between the respective active-site base, substrate molecules, and FAD. These likely differentiate NAO from the homologues and, consequently, are proposed to result in the unique reaction mechanism of NAO.
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PMID:Crystal structures of nitroalkane oxidase: insights into the reaction mechanism from a covalent complex of the flavoenzyme trapped during turnover. 1643 Feb 10

The three-dimensional structure of rat-liver acyl-CoA oxidase-II (ACO-II) in a complex with a C12-fatty acid was solved by the molecular replacement method based on the uncomplexed ACO-II structure. The crystalline form of the complex was obtained by cocrystallization of ACO-II with dodecanoyl-CoA. The crystalline complex possessed, in the active-site crevice, only the fatty acid moiety that had been formed through hydrolysis of the thioester bond. The overall dimeric structure and the folding pattern of each subunit are essentially superimposable on those of uncomplexed ACO-II. The active site including the flavin ring of FAD, the crevice embracing the fatty acyl moiety, and adjacent amino acid side chains are superimposably conserved with the exception of Glu421, whose carboxylate group is tilted away to accommodate the fatty acid. One of the carboxyl oxygens of the bound fatty acid is hydrogen-bonded to the amide hydrogen of Glu421, the presumed catalytic base, and to the ribityl 2'-hydroxyl group of FAD. This hydrogen-bonding network correlates well with the substrate recognition/activation in acyl-CoA dehydrogenase. The binding mode of C12-fatty acid suggests that the active site does not close upon substrate binding, but remains spacious during the entire catalytic process, the oxygen accessibility in the oxidative half-reaction thereby being maintained.
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PMID:Three-dimensional structure of rat-liver acyl-CoA oxidase in complex with a fatty acid: insights into substrate-recognition and reactivity toward molecular oxygen. 1667 80

Electron transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO) is a 4Fe4S flavoprotein located in the inner mitochondrial membrane. It catalyzes ubiquinone (UQ) reduction by ETF, linking oxidation of fatty acids and some amino acids to the mitochondrial respiratory chain. Deficiencies in ETF or ETF-QO result in multiple acyl-CoA dehydrogenase deficiency, a human metabolic disease. Crystal structures of ETF-QO with and without bound UQ were determined, and they are essentially identical. The molecule forms a single structural domain. Three functional regions bind FAD, the 4Fe4S cluster, and UQ and are closely packed and share structural elements, resulting in no discrete structural domains. The UQ-binding pocket consists mainly of hydrophobic residues, and UQ binding differs from that of other UQ-binding proteins. ETF-QO is a monotopic integral membrane protein. The putative membrane-binding surface contains an alpha-helix and a beta-hairpin, forming a hydrophobic plateau. The UQ-flavin distance (8.5 A) is shorter than the UQ-cluster distance (18.8 A), and the very similar redox potentials of FAD and the cluster strongly suggest that the flavin, not the cluster, transfers electrons to UQ. Two possible electron transfer paths can be envisioned. First, electrons from the ETF flavin semiquinone may enter the ETF-QO flavin one by one, followed by rapid equilibration with the cluster. Alternatively, electrons may enter via the cluster, followed by equilibration between centers. In both cases, when ETF-QO is reduced to a two-electron reduced state (one electron at each redox center), the enzyme is primed to reduce UQ to ubiquinol via FAD.
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PMID:Structure of electron transfer flavoprotein-ubiquinone oxidoreductase and electron transfer to the mitochondrial ubiquinone pool. 1705 Jun 91

A novel acyl-CoA dehydrogenase that initiates beta-oxidation of the side chains of phenylacyl-CoA compounds by Pseudomonas putida was induced by growth with phenylhexanoate as carbon source. It was identified as the product of gene PP_0368, which was cloned and overexpressed in Escherichia coli. This phenylacyl-CoA dehydrogenase was found to be dimeric with a subunit molecular mass of 66 kDa, to contain FAD and to be active with phenylacyl-CoA substrates having side chains from four to at least 11 carbon atoms. The same enzyme was induced by the aliphatic alkanoate octanoate. The optimal aliphatic substrates for the enzyme were palmitoyl-CoA and stearoyl-CoA, a property shared with mammalian very-long-chain acyl-CoA dehydrogenases. The FAD in the enzyme was reduced by aromatic and aliphatic substrates, with changes to the oxidation-reduction potential. Chemical reduction by dithionite ion and oxidation by ferricyanide ion showed that the enzyme can accept four electrons: two to reduce the flavin and two to slowly reduce an unknown acceptor, which in its reduced form interacts with the oxidized flavin in a charge-transfer complex. The experiments identify for the first time an acyl-CoA dehydrogenase that oxidizes the activated forms of aromatic acids similar to those used to first demonstrate the biological beta-oxidation of fatty acids.
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PMID:Identification and properties of an inducible phenylacyl-CoA dehydrogenase in Pseudomonas putida KT2440. 1755 93

The intramolecular and intermolecular perturbation on the electronic state of FAD was investigated by FTIR spectroscopy by using the C=O stretching vibrations as probes in D(2)O solution. Natural and artificial FADs, i.e. 8-CN-, 8-Cl-, 8-H-, 8-OCH(3)-, and 8-NH(2)-FAD labelled by 2-(13)C, (18)O=C(2), or 4,10a-(13)C(2) were used for band assignments. The C(2)=O and C(4)=O stretching vibrations of oxidized FAD were shifted systematically by the substitution at the 8-position, i.e. the stronger the electron-donating ability (NH(2) > OCH(3) > CH(3) > H > Cl > CN) of the substituent, the lower the wavenumber region where both the C(2)=O and C(4)=O bands appear. In contrast, the C(4)=O band of anionic reduced FAD scarcely shifted. The 1,645-cm(-1) band containing C(2)=O stretching vibration shifted to 1,630 cm(-1) in the medium-chain acyl-CoA dehydrogenase (MCAD)-bound state, which can be explained by hydrogen bonds at C(2)=O of the flavin ring. The band was observed at 1,607 cm(-1) in the complex of MCAD with 3-thiaoctanoyl-CoA. The 23 cm(-1) shift was explained by the charge-transfer interaction between oxidized flavin and the anionic acyl-CoA. In the case of electron-transferring flavoprotein, two bands associated with the C(4)=O stretching vibration were obtained at 1,712 and 1,686 cm(-1), providing evidence for the multiple conformations of the protein.
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PMID:Intramolecular and intermolecular perturbation on electronic state of FAD free in solution and bound to flavoproteins: FTIR spectroscopic study by using the C = O stretching vibrations as probes. 1787 56

Very-long-chain acyl-CoA dehydrogenase (VLCAD) is a member of the family of acyl-CoA dehydrogenases (ACADs). Unlike the other ACADs, which are soluble homotetramers, VLCAD is a homodimer associated with the mitochondrial membrane. VLCAD also possesses an additional 180 residues in the C terminus that are not present in the other ACADs. We have determined the crystal structure of VLCAD complexed with myristoyl-CoA, obtained by co-crystallization, to 1.91-A resolution. The overall fold of the N-terminal approximately 400 residues of VLCAD is similar to that of the soluble ACADs including medium-chain acyl-CoA dehydrogenase (MCAD). The novel C-terminal domain forms an alpha-helical bundle that is positioned perpendicular to the two N-terminal helical domains. The fatty acyl moiety of the bound substrate/product is deeply imbedded inside the protein; however, the adenosine pyrophosphate portion of the C14-CoA ligand is disordered because of partial hydrolysis of the thioester bond and high mobility of the CoA moiety. The location of Glu-422 with respect to the C2-C3 of the bound ligand and FAD confirms Glu-422 to be the catalytic base. In MCAD, Gln-95 and Glu-99 form the base of the substrate binding cavity. In VLCAD, these residues are glycines (Gly-175 and Gly-178), allowing the binding channel to extend for an additional 12A and permitting substrate acyl chain lengths as long as 24 carbons to bind. VLCAD deficiency is among the more common defects of mitochondrial beta-oxidation and, if left undiagnosed, can be fatal. This structure allows us to gain insight into how a variant VLCAD genotype results in a clinical phenotype.
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PMID:Structural basis for substrate fatty acyl chain specificity: crystal structure of human very-long-chain acyl-CoA dehydrogenase. 1822 65


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