4-Thia-trans-2-alkenoyl-CoA derivatives: properties and enzymic reactions

Lau, Sze Mei; Brantley, Richard K.; Thorpe, Colin

doi:10.1021/bi00446a043

Cited by 51 publications

(55 citation statements)

References 43 publications

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“…Although the heteroatom substitution in 4-thia-enoyl-CoA analogues appears to be a conservative change which is readily tolerated by the medium-chain acylCoA dehydrogenase (9,30), it might be argued that the effects seen in Figures 1 and 2 are peculiar to these ligands. However, data with the pig kidney medium-chain enzyme and the rather bulky indoleacryloyl-CoA (39) can be interpreted in terms of just such a pH-dependent change in polarization (9).…”

Section: -Thia-trans-2-enoyl-coa Analogues: Active Site Probesmentioning

confidence: 99%

“…4-Thia-trans-2-pentenoyl-, -octenoyl-, -dodecenoyl-, and -tridecenoyl-CoA were made by acyl-CoA-mediated oxidation of the corresponding CoA substrates (30). Cinnamoyl-CoA (9) and octyl-SCoA (31) were prepared as described previously.…”

Section: Methodsmentioning

confidence: 99%

“…In free solution, 4-thia-trans-2-enoyl-CoA product analogues (e.g., compounds 3 and 4, Chart 1) show a strong absorbance maximum at 312 nm (11,30). When bound to the dehydrogenase (Scheme 3), they can exist either in a largely unpolarized form, absorbing at the same wavelength, or in a largely polarized form peaking at 342 nm (9).…”

Section: -Thia-trans-2-enoyl-coa Analogues: Active Site Probesmentioning

confidence: 99%

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Protonic Equilibria in the Reductive Half-Reaction of the Medium-Chain Acyl-CoA Dehydrogenase

1998

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Oxidation of thioester substrates in the medium-chain acyl-CoA dehydrogenase involves R-proton abstraction by the catalytic base, Glu376, with transfer of a -hydride equivalent to the flavin prosthetic group. Polarization of bound acyl-CoA derivatives by the recombinant human liver enzyme has been studied with 4-thia-trans-2-enoyl-CoA analogues. Polarization is maximal at low pH, with an apparent pK of 9.2 for complexes with the C8 analogue, and progressively lower pK values as the length of the chain increases. This pH effect reflects ionization of the catalytic base, since polarization of a variety of enoyl-CoA analogues by the Glu376Gln mutant is pH independent. Binding of these ligands is accompanied by uptake of about 1 proton with the wild-type enzyme, but only about 0.1 proton with the Glu376Gln mutant. Rapid reaction studies show that proton uptake with the wild-type enzyme occurs at the same rate as polarization of the enoyl-CoA thioester, but is much slower than the initial ligand binding step. Studies with 6-OH-FAD-substituted enzyme show that this isomerization reaction also influences the flavin prosthetic group inducing deprotonation to the green anionic form. The failure of the bound thioether analogue, octyl-SCoA, to elicit pK shifts to flavin and Glu376 shows the importance of the thioester carbonyl oxygen in modulating key properties of the medium-chain enzyme. The role of thioester-mediated desolvation within the active site of the acyl-CoA dehydrogenases is discussed.The reductive half-reaction in the acyl-CoA dehydrogenases involves abstraction of the pro-R-R-proton of a bound acyl-CoA thioester with elimination of the pro-R--hydrogen as a hydride equivalent to the N-5 position of the flavin. The reaction appears concerted with normal (Scheme 1) substrates (1-5). The transition state for the dehydrogenation reaction is likely to have appreciable enolate character as negative charge migrates from the carboxylate base through the thioester to the flavin prosthetic group (6-10) (Scheme 2). Substitution of the C-3 methylene group in substrate analogues such as compounds 1 and 2 in Chart 1 precludes hydride transfer, but proton abstraction leads to the generation of strongly absorbing enolate to flavin chargetransfer complexes (7,11,12). These studies illustrate the profound stabilization of the enolates of these weakly acidic substrate analogues (with pK values lowered by 8-12 units; 7, 11, 12) on binding to the enzyme. The acidification of normal thioester substrates has been suggested to be even greater (12). The crystal structure of the medium-chain acylCoA dehydrogenase complexed with acyl-CoA substrates (13) suggests that the developing enolate might be stabilized in part by two hydrogen bonds: one from the 2′-OH of the ribityl side chain of FAD and one from a peptide N-H group to the substrate carbonyl oxygen (7,10,13; heavy dashed lines in Scheme 2). Thus, removal of one of these interactions by reconstitution of the enzyme with 2′-deoxy-FAD leads to a profound (g10 6 -fold) sl...

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Section: -Thia-trans-2-enoyl-coa Analogues: Active Site Probesmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: -Thia-trans-2-enoyl-coa Analogues: Active Site Probesmentioning

confidence: 99%

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Protonic Equilibria in the Reductive Half-Reaction of the Medium-Chain Acyl-CoA Dehydrogenase

1998

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“…The 4-thia FA can undergo one cycle of mitochondrial β-oxidation, but the alkyl-thioacryloyl-CoA formed in the process are poor substrates for both mitochondrial hydratase (15) and for CPT-II (16). Consequently, they accumulate in the mitochondrial matrix, where they inhibit normal FA oxidation (17).…”

mentioning

confidence: 98%

Thia fatty acids with the sulfur atom in even or odd positions have opposite effects on fatty acid catabolism

Dyrøy

Wergedahl

Skorve

et al. 2006

Lipids

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As tools for mechanistic studies on lipid metabolism, with the long-term goal of developing a drug for the treatment of lipid disorders, thia FA with the sulfur atom inserted at positions 3-9 from the carboxyl group were fed to male Wistar rats for 1 wk to determine their impact on key parameters in lipid metabolism and hepatic levels of thia FA metabolites. Thia FA with the sulfur atom in even positions decreased hepatic and cardiac mitochondrial beta-oxidation and profoundly increased hepatic and cardiac TAG levels. The plasma TAG level was unchanged and the hepatic acyl-CoA oxidase activity increased. In contrast, thia FA with the sulfur atom in odd positions, especially 3-thia FA, tended to increase hepatic and cardiac FA oxidation and acyl-CoA oxidase and carnitine palmitoyltransferase-II activities, and decreased the plasma TAG levels. The effects seem to be related to differences in the catabolic rate of the thia FA. Differences between the two groups of acids were also observed with respect to the regulation of genes involved in FA transport and catabolism. Feeding experiments with 3- and 4-thia FA in combination indicated that the 4-thia FA partly attenuated the effects of the 3-thia FA on mitochondrial FA oxidation and the hepatic TAG level. In summary, the position of the sulfur atom in the alkyl chain, especially whether it is placed in the even or odd position, is crucial for the biological effect of the thia FA.

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“…The results are shown in Figure 2. As reported earlier [5,7,12,[20][21][22][23], the reductive half-reaction of the enzyme with both butyryl-CoA and octanoyl-CoA as substrates shows a biphasic decrease in absorption at 450 nm, although such profiles originate from different microscopic mechanisms (see the Discussion section).…”

Section: Reductive Half-reaction Of Hmcadmentioning

confidence: 59%

Functional role of a distal (3′-phosphate) group of CoA in the recombinant human liver medium-chain acyl-CoA dehydrogenase-catalysed reaction

Peterson

Srivastava

1997

Biochemical Journal

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The X-ray crystallographic structure of medium-chain acyl-CoA dehydrogenase (MCAD)-octenoyl-CoA complex reveals that the 3h-phosphate group of CoA is confined to the exterior of the protein structure [approx. 15 A H (1.5 nm) away from the enzyme active site], and is fully exposed to the outside solvent environment. To ascertain whether such a distal (3h-phosphate) fragment of CoA plays any significant role in the enzyme catalysis, we investigated the recombinant human liver MCAD (HMCAD)-catalysed reaction by using normal (phospho) and 3h-phosphate-truncated (dephospho) forms of octanoyl-CoA and butyryl-CoA substrates. The steady-state kinetic data revealed that deletion of the 3h-phosphate group from octanoyl-CoA substrate increased the turnover rate of the enzyme to about one-

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4-Thia-trans-2-alkenoyl-CoA derivatives: properties and enzymic reactions

Cited by 51 publications

References 43 publications

Protonic Equilibria in the Reductive Half-Reaction of the Medium-Chain Acyl-CoA Dehydrogenase

Protonic Equilibria in the Reductive Half-Reaction of the Medium-Chain Acyl-CoA Dehydrogenase

Thia fatty acids with the sulfur atom in even or odd positions have opposite effects on fatty acid catabolism

Functional role of a distal (3′-phosphate) group of CoA in the recombinant human liver medium-chain acyl-CoA dehydrogenase-catalysed reaction

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