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)

Acyl-CoA oxidase (ACO) catalyzes the first and rate-determining step of the peroxisomal beta-oxidation of fatty acids. The crystal structure of ACO-II, which is one of two forms of rat liver ACO (ACO-I and ACO-II), has been solved and refined to an R-factor of 20.6% at 2.2-A resolution. The enzyme is a homodimer, and the polypeptide chain of the subunit is folded into the N-terminal alpha-domain, beta-domain, and C-terminal alpha-domain. The X-ray analysis showed that the overall folding of ACO-II less C-terminal 221 residues is similar to that of medium-chain acyl-CoA dehydrogenase (MCAD). However, the N-terminal alpha- and beta-domains rotate by 13 with respect to the C-terminal alpha-domain compared with those in MCAD to give a long and large crevice that accommodates the cofactor FAD and the substrate acyl-CoA. FAD is bound to the crevice between the beta- and C-terminal domains with its adenosine diphosphate portion interacting extensively with the other subunit of the molecule. The flavin ring of FAD resides at the active site with its si-face attached to the beta-domain, and is surrounded by active-site residues in a mode similar to that found in MCAD. However, the residues have weak interactions with the flavin ring due to the loss of some of the important hydrogen bonds with the flavin ring found in MCAD. The catalytic residue Glu421 in the C-terminal alpha-domain seems to be too far away from the flavin ring to abstract the alpha-proton of the substrate acyl-CoA, suggesting that the C-terminal domain moves to close the active site upon substrate binding. The pyrimidine moiety of flavin is exposed to the solvent and can readily be attacked by molecular oxygen, while that in MCAD is protected from the solvent. The crevice for binding the fatty acyl chain is 28 A long and 6 A wide, large enough to accommodate the C23 acyl chain.
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PMID:Three-dimensional structure of the flavoenzyme acyl-CoA oxidase-II from rat liver, the peroxisomal counterpart of mitochondrial acyl-CoA dehydrogenase. 1187 65

The active site residue, Glu-376, of medium-chain acyl-CoA dehydrogenase (MCAD) has been known to abstract the alpha-proton from acyl-CoA substrates during the course of the reductive half-reaction. The site-specific mutation of Glu-376-->Gln(E376Q) slows down the octanoyl-CoA-dependent reductive half-reaction of the enzyme by about 5 orders of magnitude due to impairment in the proton-transfer step. To test whether the carboxyl group of Glu-376 exclusively serves as the active site base (for abstracting the alpha-proton) during the enzyme catalysis, we undertook a detailed kinetic investigation of the enzyme-ligand interaction and enzyme catalysis, utilizing octanoyl-CoA/octenoyl-CoA as a physiological substrate/product pair and the wild-type and E376Q mutant enzymes as the catalysts. The transient kinetic data revealed that the E376Q mutation not only impaired the rate of octanoyl-CoA-dependent reduction of the enzyme-bound FAD, but also impaired the association and dissociation rates for the binding of the reaction product, octenoyl-CoA. Besides, the E376Q mutation correspondingly impaired the kinetic profiles for the quenching of the intrinsic protein fluorescence during the course of the above diverse (i.e., "chemistry" versus "physical interaction") processes. A cumulative account of the experimental data led to the suggestion that the carboxyl group of Glu-376 of MCAD is intimately involved in modulating the microscopic environment (protein conformation) of the enzyme's active site during the course of ligand binding and catalysis. Arguments are presented that the electrostatic interactions among Glu-376, FAD, and CoA-ligands are responsible for structuring the enzyme's active site cavity in the ground and transition states of the enzyme during the above physicochemical processes.
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PMID:Beyond the proton abstracting role of Glu-376 in medium-chain acyl-CoA dehydrogenase: influence of Glu-376-->Gln substitution on ligand binding and catalysis. 1192 26

Acryloyl-CoA reductase from Clostridium propionicum catalyses the irreversible NADH-dependent formation of propionyl-CoA from acryloyl-CoA. Purification yielded a heterohexadecameric yellow-greenish enzyme complex [(alpha2betagamma)4; molecular mass 600 +/- 50 kDa] composed of a propionyl-CoA dehydrogenase (alpha2, 2 x 40 kDa) and an electron-transferring flavoprotein (ETF; beta, 38 kDa; gamma, 29 kDa). A flavin content (90% FAD and 10% FMN) of 2.4 mol per alpha2betagamma subcomplex (149 kDa) was determined. A substrate alternative to acryloyl-CoA (Km = 2 +/- 1 microm; kcat = 4.5 s-1 at 100 microm NADH) is 3-buten-2-one (methyl vinyl ketone; Km = 1800 microm; kcat = 29 s-1 at 300 microm NADH). The enzyme complex exhibits acyl-CoA dehydrogenase activity with propionyl-CoA (Km = 50 microm; kcat = 2.0 s-1) or butyryl-CoA (Km = 100 microm; kcat = 3.5 s-1) as electron donor and 200 microm ferricenium hexafluorophosphate as acceptor. The enzyme also catalysed the oxidation of NADH by iodonitrosotetrazolium chloride (diaphorase activity) or by air, which led to the formation of H2O2 (NADH oxidase activity). The N-terminus of the dimeric propionyl-CoA dehydrogenase subunit is similar to those of butyryl-CoA dehydrogenases from several clostridia and related anaerobes (up to 55% sequence identity). The N-termini of the beta and gamma subunits share 40% and 35% sequence identities with those of the A and B subunits of the ETF from Megasphaera elsdenii, respectively, and up to 60% with those of putative ETFs from other anaerobes. Acryloyl-CoA reductase from C. propionicum has been characterized as a soluble enzyme, with kinetic properties perfectly adapted to the requirements of the organism. The enzyme appears not to be involved in anaerobic respiration with NADH or reduced ferredoxin as electron donors. There is no relationship to the trans-2-enoyl-CoA reductases from various organisms or the recently described acryloyl-CoA reductase activity of propionyl-CoA synthase from Chloroflexus aurantiacus.
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PMID:Acryloyl-CoA reductase from Clostridium propionicum. An enzyme complex of propionyl-CoA dehydrogenase and electron-transferring flavoprotein. 1260 23

The role of the oxyanion hole in the reaction catalyzed by pig medium-chain acyl-CoA dehydrogenase (pMCAD) has been investigated using enzyme reconstituted with 2'-deoxy-FAD. The k(cat) (18.8 +/- 0.5 s(-1)) and K(m) (2.5 +/- 0.4 microM) values for the oxidation of n-octanoyl-CoA (C(8)-CoA) by WT pMCAD recombinantly expressed in Escherichia coli are similar to those of native pMCAD isolated from pig kidney. In agreement with previous studies [Engst et al. (1999) Biochemistry 38, 257-267], reconstitution of the WT enzyme with 2'-deoxy-FAD causes a large (400-fold) decrease in k(cat) but has little effect on K(m). To investigate the molecular basis for the alterations in activity resulting from changes in hydrogen bonding between the substrate and the enzyme's oxyanion hole, the structure of the product analogue hexadienoyl-CoA (HD-CoA) bound to the 2'-deoxy-FAD-reconstituted enzyme has been probed by Raman spectroscopy. Importantly, while WT pMCAD causes a 27 cm(-1) decrease in the vibrational frequency of the HD enone band, from 1595 to 1568 cm(-1), the enone band is only shifted 10 cm(-1) upon binding HD-CoA to 2'-deoxy-FAD pMCAD. Thus, removal of the 2'-ribityl hydroxyl group results in a substantial reduction in the ability of the enzyme to polarize the ground state of the ES complex. On the basis of an analysis of a similar system, it is estimated that ground state destabilization is reduced by up to 17 kJ mol(-1), while the activation energy for the reaction is raised 15 kJ mol(-1). In addition, removal of the 2'-ribityl hydroxyl reduces the redox potential shift that is induced by HD-CoA binding from 18 to 11 kJ mol(-1). Consequently, while ligand polarization caused by hydrogen bonding in the oxyanion hole is intimately linked to substrate turnover, additional factors must be responsible for ligand-induced changes in redox potential. Finally, while replacement of the catalytic base E376 with Gln abolishes the ability of the enzyme to catalyze substrate oxidation and to catalyze the exchange of the C(8)-CoA alpha-protons with solvent deuterium, the 2'-deoxy-FAD-reconstituted enzyme catalyzes alpha-proton exchange at a rate (k(exc)) of 0.085 s(-1), which is only 4-fold slower than k(exc) for WT pMCAD (0.35 s(-1)). Thus, either the oxyanion hole plays only a minor role in stabilizing the transition state for alpha-proton exchange, in contrast to its role in substrate oxidation, or the value of k(exc) for WT pMCAD reflects a process such as exchange of the E376 COOH proton with solvent.
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PMID:Probing hydrogen-bonding interactions in the active site of medium-chain acyl-CoA dehydrogenase using Raman spectroscopy. 1452 97

Acyl-CoA dehydrogenases and acyl-CoA oxidases are two closely related FAD-containing enzyme families that are present in mitochondria and peroxisomes, respectively. They catalyze the dehydrogenation of acyl-CoA thioesters to the corresponding trans-2-enoyl-CoA. This review examines the structure of medium chain acyl-CoA dehydrogenase, as a representative of the dehydrogenase family, with respect to the catalytic mechanism and its broad chain length specificity. Comparing the structures of four other acyl-CoA dehydrogenases provides further insights into the structural basis for the substrate specificity of each of these enzymes. In addition, the structure of peroxisomal acyl-CoA oxidase II from rat liver is compared to that of medium chain acyl-CoA dehydrogenase, and the structural basis for their different oxidative half reactions is discussed.
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PMID:Acyl-CoA dehydrogenases and acyl-CoA oxidases. Structural basis for mechanistic similarities and differences. 1472 75

The pKa value of a substrate analogue 3-thiaoctanoyl-CoA at alphaC-H is known to drop from ca. 16 in the free state to 5-6 upon binding to medium-chain acyl-CoA dehydrogenase (MCAD). The molecular mechanism underlying this phenomenon was investigated by taking advantage of artificial FADs, i.e., 8-CN-, 7,8-Cl2-, 8-Cl-, 8-OCH3-, 8-NH2-, ribityl-2'-deoxy-8-CN-, and ribityl-2'-deoxy-8-Cl-FADs, reconstituted into MCAD. The stronger the electron-withdrawing ability of the substituent, the smaller the pKa value became [e.g., 7.4 (8-NH2-FAD) and 4.0 (8-CN-FAD)], suggesting that the flavin ring itself affects the pKa value of the ligand via a charge-transfer interaction with the ligand. The destruction of the hydrogen bond between the thioester C(1)=O and the ribityl-2'-OH of FAD raised the pKa by ca. 2.5 units. These results indicate that the interaction between the ligand and the flavin ring also serves to lower the pKa of the ligand, in addition to the hydrogen bonds at C(1)=O of the ligand.
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PMID:Molecular mechanism of the drop in the pKa of a substrate analog bound to medium-chain acyl-CoA dehydrogenase: implications for substrate activation. 1476 72

The crystal structure of the human electron transferring flavoprotein (ETF).medium chain acyl-CoA dehydrogenase (MCAD) complex reveals a dual mode of protein-protein interaction, imparting both specificity and promiscuity in the interaction of ETF with a range of structurally distinct primary dehydrogenases. ETF partitions the functions of partner binding and electron transfer between (i) the recognition loop, which acts as a static anchor at the ETF.MCAD interface, and (ii) the highly mobile redox active FAD domain. Together, these enable the FAD domain of ETF to sample a range of conformations, some compatible with fast interprotein electron transfer. Disorders in amino acid or fatty acid catabolism can be attributed to mutations at the protein-protein interface. Crucially, complex formation triggers mobility of the FAD domain, an induced disorder that contrasts with general models of protein-protein interaction by induced fit mechanisms. The subsequent interfacial motion in the MCAD.ETF complex is the basis for the interaction of ETF with structurally diverse protein partners. Solution studies using ETF and MCAD with mutations at the protein-protein interface support this dynamic model and indicate ionic interactions between MCAD Glu(212) and ETF Arg alpha(249) are likely to transiently stabilize productive conformations of the FAD domain leading to enhanced electron transfer rates between both partners.
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PMID:Extensive domain motion and electron transfer in the human electron transferring flavoprotein.medium chain Acyl-CoA dehydrogenase complex. 1515 92

Mitochondrial medium-chain acyl-CoA dehydrogenase is a key enzyme for the beta oxidation of fatty acids, and the deficiency of this enzyme in patients has been previously reported. We found that the enzyme has intrinsic isomerase activity, which was confirmed using incubation followed with HPLC analysis. The isomerase activity of the enzyme was thoroughly characterized through studies of kinetics, substrate specificity, pH dependence, and enzyme inhibition. E376 mutants were constructed, and mutant enzymes were purified and characterized. It was shown that E376 is the catalytic residue for both dehydrogenase and isomerase activities of the enzyme. The isomerase activity of medium-chain acyl-CoA dehydrogenase is probably a spontaneous process driven by thermodynamic equilibrium with the formation of a conjugated structure after deprotonation of substrate alpha proton. The energy level of the transition state may be lowered by a stable dienolate intermediate, which gains further stabilization via charge transfer with the electron-deficient FAD cofactor of the enzyme. This raises the question as to whether the dehydrogenase might function as an isomerase in vivo in conditions in which the activity of the isomerase is decreased.
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PMID:Intrinsic isomerase activity of medium-chain acyl-CoA dehydrogenase. 1585 Apr 6

Crystal structures of protein complexes with electron-transferring flavoprotein (ETF) have revealed a dual protein-protein interface with one region serving as anchor while the ETF FAD domain samples available space within the complex. We show that mutation of the conserved Glu-165beta in human ETF leads to drastically modulated rates of interprotein electron transfer with both medium chain acyl-CoA dehydrogenase and dimethylglycine dehydrogenase. The crystal structure of free E165betaA ETF is essentially identical to that of wild-type ETF, but the crystal structure of the E165betaA ETF.medium chain acyl-CoA dehydrogenase complex reveals clear electron density for the FAD domain in a position optimal for fast interprotein electron transfer. Based on our observations, we present a dynamic multistate model for conformational sampling that for the wild-type ETF. medium chain acyl-CoA dehydrogenase complex involves random motion between three distinct positions for the ETF FAD domain. ETF Glu-165beta plays a key role in stabilizing positions incompatible with fast interprotein electron transfer, thus ensuring high rates of complex dissociation.
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PMID:Stabilization of non-productive conformations underpins rapid electron transfer to electron-transferring flavoprotein. 1597 18

A gene (PP2216) that codes for an acyl-CoA dehydrogenase was cloned from Pseudomonas putida strain KT2240 and over-expressed in Escherichia coli, and the recombinant enzyme purified and characterised. The enzyme is tetrameric with one FAD per subunit of molecular mass 40,500 Da. An anaerobic titration with sodium dithionite showed that the enzyme accepts two electrons. A similar titration with butyryl-CoA showed that reduction by this substrate was incomplete with 4.5 mol butyryl-CoA added per mol enzyme FAD; the equilibrium was used to calculate that the oxidation-reduction potential of the enzyme at pH 7 and 25 degrees C is 5+/-5 mV versus the standard hydrogen electrode. The enzyme shows catalytic activity with butyryl-CoA, valeryl-CoA and hexanoyl-CoA, and very low activity with heptanoyl-CoA and octanoyl-CoA; it fails to oxidise propionyl-CoA. These properties resemble those of short-chain acyl-CoA dehydrogenases from other sources. The enzyme is inactive with the CoA derivatives of all phenylalkanoates that were tested (side chains 3-8 carbon atoms) indicating that in contrast to an earlier suggestion, the enzyme is not involved in the beta-oxidation of aromatic compounds.
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PMID:The protein coded by the PP2216 gene of Pseudomonas putida KT2440 is an acyl-CoA dehydrogenase that oxidises only short-chain aliphatic substrates. 1602 85


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