Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.3.99.3 (acyl-CoA dehydrogenase)
 1,425 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mammalian electron-transferring flavoproteins have previously been reported to form the red anionic semiquinone on 1-electron reduction. This work describes a new form of electron-transferring flavoprotein (ETFB) from pig kidney which yields the blue neutral semiquinone upon photochemical, dithionite, or enzymatic reduction. ETFB appears in varying amounts as part of an established purification scheme for ETF. Both the normal form of ETF (ETFR) and ETFB show small differences in the spectra of their oxidized flavins, but no detectable differences in molecular weight or subunit composition. The catalytic activities of ETFR and ETFB are comparable when they mediate the transfer of reducing equivalents between medium chain acyl-CoA dehydrogenase and 2,6-dichlorophenolindophenol. ETFB can be converted into a form showing the characteristic red semiquinone of ETFR by full reduction at pH 6.5 or by preparation of the apoprotein and reconstitution with FAD. In contrast, no conditions for the conversion of red to blue forms of ETF have been found. ETFB contains substoichiometric levels of an unusual FAD analogue which yields a pink flavin species on photochemical or dithionite reduction. The evidence presented suggests that ETFB contains a labile factor or protein modification which is irreversibly lost on conversion to ETFR. The possible physiological significance of these data is discussed.
 ...
PMID:A new form of mammalian electron-transferring flavoprotein. 173 21

Different forms of rat liver medium-chain acyl CoA dehydrogenase (MCAD) (EC 1.3.99.3) were produced in Escherichia coli carrying expression plasmids (pRMCADm-1 approximately 9) differing at the 5'-region of the cDNA. The proteins expressed could be readily extracted from the cells. The protein (approximately 44 kDa) directed by pRMCADm-3 showed the highest activity and was readily purified to homogeneity. The purified enzyme contained non-covalently bound FAD and was similar to rat liver mitochondrial enzyme in all respects examined. The purified protein (approximately 45 kDa) directed by pRMCADm-1 did not contain FAD and showed no enzymatic activity. Therefore, the leader peptide disturbs the binding of FAD to the apoprotein. The purified protein (approximately 40 kDa) directed by pRMCADm-6 did not contain FAD. Thus, the deletion of the NH2-terminal portion of the apoprotein to some extent results in its inability to combine with FAD.
 ...
PMID:Structurally different rat liver medium-chain acyl CoA dehydrogenases directed by complementary DNAs differing in their 5'-region. 202 27

Aspects of the binding and dehydrogenation of acyl-CoA thiol esters by the general acyl-CoA dehydrogenase from pig liver were investigated using a dead-end inhibitor, S-octyl-CoA, several alternate substrates, and three active site-directed inhibitors. Experiments with S-octyl-CoA indicate that the carbonyl group of acyl-CoA thiol esters is not absolutely required for binding to the enzyme. However, the mode of binding of the 8-carbon thiol ether can be distinguished from the mode of binding of the enoyl-CoA product, octenoyl-CoA. Octanoyl pantetheine, octanoyl-etheno-CoA, and octanoyl-3'-dephospho-CoA are alternate substrates of the dehydrogenase. Steady state kinetic constants obtained with these alternate substrates indicate that the adenosine 5'-diphosphate, but not the 3'-phosphate, of the nucleotide moiety of acyl-CoA substrates contribute to the tight binding of the substrates. The substrate analogs 3'-butynoyl-CoA and 3-octynoyl-CoA are active site-directed, mechanism-based irreversible inhibitors of the dehydrogenase. These inhibitors covalently modify the apoprotein rather than the flavin. This finding and the fact that 2,3-octadienoyl-CoA also completely and irreversibly inhibits the enzyme indicate that th 3-acetylenic thiol esters inhibit the enzyme by a mechanism involving: (1) base-catalyzed abstraction of a protein at C-2 followed by isomerization to the allene carbanion, (2) protonation of the carbanion, and (3) attack of a nucleophile in the enzyme-active site on C-3 of the 2,3-dienoyl-CoA. The data show that the alkynoyl-CoA's are activated and bound at the active site of the enzyme. The results suggest that abstraction of a proton at C-2 of acyl-CoA substrates is the initial step in the catalytic pathway of dehydrogenation of substrates by the enzyme.
 ...
PMID:Enzyme-activated inhibitors, alternate substrates, and a dead end inhibitor of the general acyl-CoA dehydrogenase. 744 May 36

Electron-transfer flavoprotein (ETF) serves as an intermediate electron carrier between primary flavoprotein dehydrogenases and terminal respiratory chains in mitochondria and prokaryotic cells. The three-dimensional structures of human and Paracoccus denitrificans ETFs determined by X-ray crystallography indicate that the 4'-hydroxyl of the ribityl side chain of FAD is hydrogen bonded to N(1) of the flavin ring. We have substituted 4'-deoxy-FAD for the native FAD and investigated the analog-containing ETF to determine the role of this rare intra-cofactor hydrogen bond. The binding constants for 4'-deoxy-FAD and FAD with the apoprotein are very similar, and the energy of binding differs by only 2 kJ/mol. The overall two-electron oxidation-reduction potential of 4'-deoxy-FAD in solution is identical to that of FAD. However, the potential of the oxidized/semiquinone couple of the ETF containing 4'-deoxy-FAD is 0.116 V less than the oxidized/semiquinone couple of the native protein. These data suggest that the 4'-hydoxyl-N(1) hydrogen bond stabilizes the anionic semiquinone in which negative charge is delocalized over the N(1)-C(2)O region. Transfer of the second electron to 4'-deoxy-FAD reconstituted ETF is extremely slow, and it was very difficult to achieve complete reduction of the flavin semiquinone to the hydroquinone. The turnover of medium chain acyl-CoA dehydrogenase with native ETF and ETF containing the 4'-deoxy analogue was essentially identical when the reduced ETF was recycled by reduction of 2,6-dichlorophenolindophenol. However, the steady-state turnover of the dehydrogenase with 4'-deoxy-FAD was only 23% of the turnover with native ETF when ETF semiquinone formation was assayed directly under anaerobic conditions. This is consistent with the decreased potential of the oxidized semiquinone couple of the analog-containing ETF. ETF containing 4'-deoxy-FAD neither donates to nor accepts electrons from electron-transfer flavoprotein ubiquinone oxidoreductase (ETF-QO) at significant rates (</=0.5% the wild-type rates). These results indicate that the 4'-hydroxyl-N(1) hydrogen bond plays a major role in the stabilization of the anionic semiquinone and anionic hydroquinone oxidation states of ETF and that this hydrogen bond may provide a pathway for electron transfer between the ETF flavin and the flavin of ETF-QO.
 ...
PMID:The intraflavin hydrogen bond in human electron transfer flavoprotein modulates redox potentials and may participate in electron transfer. 1042 53

Squalene, a hydrocarbon involved in cholesterol biosynthesis, is an abundant component in virgin olive oil. Previous studies showed that its administration decreased atherosclerosis and steatosis in male apoE knock-out mice. To study the effect of squalene on mitochondrial proteins in fatty liver, 1 g/kg/day of this isoprenoid was administered to those mice. After 10 weeks, hepatic fat was assessed and protein extracts from mitochondria enriched fractions from control and squalene-treated animals were analyzed by 2D-DIGE. Spots exhibiting significant differences were identified by MS analysis. Squalene administration modified the expression of eighteen proteins involved in different metabolic processes, 12 associated with hepatic fat content. Methionine adenosyltransferase I alpha (Mat1a) and short-chain specific acyl-CoA dehydrogenase (Acads) showed significant increased and decreased transcripts, respectively, consistent with their protein changes. These mRNAs were also studied in wild-type mice receiving squalene, where Mat1a was found increased and Acads decreased. However, this mRNA was significantly increased in the absence of apolipoprotein E. These results suggest that squalene action may be executed through a complex regulation of mitochondrial protein expression, including changes in Mat1a and Acads levels. Indeed, Mat1a is a target of squalene administration while Acads reflects the anti-steatotic properties of squalene.
 ...
PMID:Proteomics and gene expression analyses of mitochondria from squalene-treated apoE-deficient mice identify short-chain specific acyl-CoA dehydrogenase changes associated with fatty liver amelioration. 2240 57