Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Treatment of yeast fatty acid synthetase with pyridoxal 5'-phosphate inhibited the enzyme. Assays of the partial activities of the pyridoxal phosphate-treated synthetase showed that only the beta-ketoacyl reductase was significantly inhibited. NADPH prevented inactivation of the enzyme by pyridoxal phosphate, indicating that pyridoxal modifies a residue near or in the beta-ketoacyl reductase site. The pyridoxal-treated synthetase shows a fluorescence spectrum with a maximum of 426 nm after uv irradiation at 325 nm. Binding of the pyridoxal phosphate to the synthetase is reversible as shown by the disappearance of the fluorescence band after dialysis of pyridoxal-treated enzyme. Reduction with NaBH4 of the pyridoxal-treated enzyme eliminates this fluorescence maximum and causes the appearance of a new band at 393 nm. These observations suggest that pyridoxal phosphate interacts with the synthetase by forming a Schiff base with lysine residue at the beta-ketoacyl reductase site. Amino acid analyses of the HCl hydrolysates of the borohydride-reduced, pyridoxal-treated synthetase showed the presence of 6 mol of N6-pyridoxal derivative of lysine per mole of fatty acid synthetase, indicating the presence of six sites of beta-ketoacyl reductase in the native enzyme. Autoradiography of sodium dodecyl sulfate-polyacrylamide gels of the pyridoxal phosphate enzyme reduced with NaB3H4 indicates that the alpha subunit contains the beta-ketoacyl reductase domain. These findings are consistent with the proposed structure of the alpha 6 beta 6 complex required for palmitoyl-CoA synthesis.
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PMID:Inactivation of yeast fatty acid synthetase by modifying the beta-ketoacyl reductase active lysine residue with pyridoxal 5'-phosphate. 641 72

Pigeon liver fatty acid synthetase was inactivated by stoichiometric concentrations of diethylpyrocarbonate (DEP). The second order rate constant for the loss of synthetase activity was similar to the value for enoyl-CoA reductase indicating that ethoxyformylation destroys the ability of the enzyme to reduce the unsaturated acyl intermediate, without significant effect on beta-ketoacyl reductase activity. NADPH provided protection to the enzyme against inactivation by DEP indicating that essential histidine residues are present at the active site. DEP-modified enzyme showed a characteristic absorption maxima at 240 nm confirming the formation of ethoxyformic histidine. The reversal of inactivation by hydroxylamine and a pKa value of 7.0 obtained from the pH-rate profile for inactivation again confirmed the specificity of DEP for histidine. Stoichiometric results showed that two moles of histidine residue per mole of enzyme are essential for the activity of FAS.
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PMID:Evidence for the essential histidine at the NADPH binding site of enoyl-CoA reductase domain of pigeon liver fatty acid synthetase. 920 89

The conformational stability of the homotetrameric Plasmodium falciparum beta-ketoacyl-ACP reductase (FabG) was determined by guanidinium chloride-induced isothermal and thermal denaturation. The reversible unfolding transitions were monitored by intrinsic fluorescence, circular dichroism (CD) spectroscopy and by measuring the enzyme activity of FabG. The denaturation profiles were analyzed to obtain the thermodynamic parameters associated with unfolding of the protein. The data confirm the simple A(4) <--> 4A model of unfolding, based on the corroboration of CD data by fluorescence transition and similar Delta G estimation for denaturation curves obtained at four different concentration of the FabG. Denaturation is well described by the linear extrapolation model for denaturant-protein interactions. In addition, the conformational stability (Delta G(s)) as well as the Delta C(p) for the protein unfolding is quite high, 22.68 kcal/mole and 5.83 kcal/(mole K), respectively, which may be a reflection of the relatively large size of the tetrameric molecule (Mr 120, 000) and a large buried hydrophobic core in the folded protein. This study provides a prototype for determining conformational stability of other members of the short-chain alcohol dehydrogenase/reductase superfamily of proteins to which PfFabG belongs.
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PMID:Conformational stability and thermodynamic characterization of homotetrameric Plasmodium falciparum beta-ketoacyl-ACP reductase. 1765 20