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)

Pig kidney medium-chain acyl-CoA dehydrogenase (EC 1.3.99.3) is irreversibly and stoichiometrically inactivated by [1-14C]-2-octynoyl coenzyme A. The linkage is stable at pH 2-6, but labile under basic conditions. The inhibitor labels a unique tryptic peptide, Ile-Tyr-Gln-Ile-Tyr-Glu-Gly-Thr-Ala-Gln-Ile-Gln-Arg, close to the C-terminus of the protein. The peptide is labeled at Glu-401 with the acyl moiety of the inhibitor but does not contain detectable coenzyme A. Both the inactivation of the dehydrogenase and the appearance of an absorption band at 800 nm show large primary deuterium isotope effects using 4,4'-dideuterio-2-octynoyl-CoA (7.3 and 6.3, respectively). Thus, 2-octynoyl-CoA is a mechanism-based inactivator of the dehydrogenase and is activated by rate-limiting gamma-proton abstraction. Glutamate-401 may be the base that abstracts the pro-R alpha-proton during the dehydrogenation of normal substrates.
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PMID:2-octynoyl coenzyme A is a mechanism-based inhibitor of pig kidney medium-chain acyl coenzyme A dehydrogenase: isolation of the target peptide. 323 92

The acyl-CoA dehydrogenases are a family of flavoenzymes with similar structure and function involved in the metabolism of fatty acids and branched chain amino acids. The degree of overlap in substrate specificity is narrow among these enzymes. The position of the catalytic glutamate, identified as Glu376 in porcine medium chain acyl-CoA dehydrogenase (MCAD), Glu254 in human isovaleryl-CoA dehydrogenase (IVD), and Glu261 in human long chain acyl-CoA dehydrogenase (LCAD), has been suggested to affect substrate chain length specificity. In this study, in vitro site-directed mutagenesis was used to investigate the effect of changing the position of the catalytic carboxylate on substrate specificity in short chain acyl-CoA dehydrogenase (SCAD). Glu368, the hypothetical active site catalytic residue of rat SCAD, was replaced with Asp, Gly, Gln, Arg, and Lys and the wild type and mutant SCADs were produced in Escherichia coli and purified. The recombinant wild type SCAD kcat/K(m) values for butyryl-hexanoyl-, and octanoyl-CoA were 220, 22, and 3.2 microM-1 min-1, respectively, while the Glu368Asp mutant gave kcat/K(m) of 81, 12, and 1.4 microM-1 min-1, respectively, for the same substrates. None of the other mutants exhibited enzyme activity. A Glu368Gly/Gly247Glu double mutant enzyme, which places the catalytic residue at a position homologous to that of LCAD, was also synthesized and purified. It showed kcat/K(m) of 9.3, 2.8, and 1.5 microM-1 min-1 with butyryl-, hexanoyl-, and octanoyl-CoA used as substrates, respectively. These results confirm the identity of Glu368 as the catalytic residue of rat SCAD and suggest that alteration of the position of the catalytic carboxylate can modify substrate specificity.
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PMID:Functional role of the active site glutamate-368 in rat short chain acyl-CoA dehydrogenase. 895 87

Sponges (Porifera) are the phylogenetically oldest metazoan organisms. From one member of the siliceous sponges, Geodia cydonium, the cDNA encoding a putative SOS protein, the AidB-like protein of the Ada system from bacteria, was isolated and characterized. The cDNA, GCaidB, comprises an open reading frame of 446 amino acid (aa) residues encoding a polypeptide with a calculated Mr of 49,335. This molecule shows high similarity to the bacterial AidB proteins from Mycobacterium tuberculosis and Escherichia coli and somewhat lower similarities to acyl-CoA dehydrogenases (ADHs) and acyl-CoA oxidases (AOXs). Northern blot analysis confirmed the presence of the complete transcript. The deduced sponge aa sequence, GC_aidB, possesses the two characteristic acyl-CoA dehydrogenase signatures 1 and 2. Incubation of the sponge with N-methyl-N'-nitro-N-nitrosoguanidine causes a strong increase in the 2.1-kb large transcript of GCaidB; maximal expression is seen after 24 h of incubation with this DNA methylating agent. ADHs and AOXs can be grouped, depending on the position of the catalytically important Glu residue, into the Glu-Gly (Glu adjacent to Gly) class and the Glu-Arg (Glu adjacent to Arg) class. The phylogenetically oldest metazoan AidB-like molecule, GC_aidB of G. cydonium, belongs to the Glu-Gly class of ADHs. Phylogenetic analyses of the Glu-Gly class enzymes, with the described AidB-like protein from G. cydonium and the bacterial AidB polypeptides, together with metazoan ADHs and AOXs, revealed that the AidB(-like) proteins diverged first from a common ancestor, while the eukaryotic AOX and ADA polypeptides as well as the GHDs appeared later. According to the analyses, the very long-chain ADHs are older than the medium-chain, short-chain, and branched-chain ADHs. Inclusion of the phylogenetical oldest member of the Glu-Arg class of enzymes, the bacterial ADH-CaiA sequence in these analyses, revealed that this class of enzymes appeared later in evolution and arose from the Glu-Gly class perhaps after gene duplication.
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PMID:Identification and expression of the SOS response, aidB-like, gene in the marine sponge Geodia cydonium: implication for the phylogenetic relationships of metazoan acyl-CoA dehydrogenases and acyl-CoA oxidases. 973 61

Glu376, the base involved in substrate alphaH+ abstraction at the active center of medium-chain acyl-CoA dehydrogenase (MCAD), has been mutated to Gln and Gly. The mutants are active; however, their rates of dehydrogenation are lowered by approximately 5 orders of magnitude. Binding of the substrate octanoyl-CoA to Glu376Gln-MCAD involves (at least) two steps. The ensuing dehydrogenation reaction that corresponds to reduction of the flavin cofactor also occurs in two phases. These are interpreted to consist of a first, reversible step, followed by a slower, practically irreversible one. For Glu376Gln-MCAD, the log of the rates of dehydrogenation increases linearly with pH (slope = 1) in the pH range of 6-10, suggesting HO- as a reactant. The rates of the same reactions in D2O have the same pD profile and reflect a solvent kinetic isotope effect (SKIE) of approximately 8.5. Glu376Gln+Glu99Gly-MCAD (studied to assess the role of Glu99 also present at the bottom of the active center cavity) has activities and activity profiles similar to those of Glu376Gln-MCAD. This excludes Glu99 as the active center base for Glu376Gln-MCAD catalysis. Proton inventories for the two phases of the dehydrogenation reaction were investigated at 4 and 25 degrees C. The inventories at 25 degrees C reflect a SKIE of approximately 4.5; the profiles are "bowl-shaped", in which a transition-state contribution predominates. The profiles for the 4 degrees C reaction are very unusual. That for the first phase can be analyzed on a two-step model with one step (80% rate-limiting) having a conformational reorganization with an isotope effect of 90-100, from small isotope effects at many protein sites, and the other step (20% rate-limiting) having an inverse isotope effect of ca. 2, characteristic of the reaction of hydroxide ion as a base. For the second phase, only a contribution from many protein sites with a KIE of approximately 4.5 is observed. The results are compatible with a very rigid active site framework that must undergo rearrangements for dehydrogenation to take place, and specifically to allow access of HO-, the reactant that must neutralize the H+ abstracted from the alphaC-H substrate. The large isotope effects are attributed to the changes in state of several H-bonds that occur during the process.
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PMID:Solvent isotope effects in reactions of human medium-chain acyl-CoA dehydrogenase active site mutants. 1728 88

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