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H Bisswanger

Publications and source records attributed to H Bisswanger.

8 recordsLinked to original sources
PubMed1992

Incorporation of the enantiomers of lipoic acid into the pyruvate dehydrogenase complex from Escherichia coli in vivo.

The uptake of 35S-labelled enantiomers of lipoic acid into cells from Escherichia coli was studied. The R-enantiomer was taken up by a factor of two more efficiently than the S-form. Autoradiography of polyacrylamide gels of partially purified pyruvate dehydrogenase complex from these cells showed that only the R-lipoic acid was covalently incorporated as a cofactor into the dihydrolipoamide acetyltransferase component of the pyruvate dehydrogenase complex.

Autoradiography↗
PubMed1990

Localization of the alpha-oxoacid dehydrogenase multienzyme complexes within the mitochondrion.

Bovine kidney mitochondria were separated into matrix and membrane fractions by treatment with digitonin and Lubrol PX. While malate dehydrogenase was found essentially in the matrix fraction, both the pyruvate and the alpha-oxoglutarate dehydrogenase multienzyme complexes remained bound to the inner membrane fraction and became solubilized only after repeated treatments with detergents. Thus both multienzyme complexes must be associated with the inner membrane rather than located within the matrix space.

Animals↗
PubMed1990

Application of high-performance liquid chromatography to the purification, disintegration and molecular mass determination of pyruvate dehydrogenase multi-enzyme complexes from different sources.

The pyruvate dehydrogenase complex is associated with the inner mitochondrial membrane. A gentle and rapid purification procedure, especially for the very unstable pyruvate dehydrogenase complex from the extremely thermophilic organism Thermus aquaticus, is described. This procedure is based essentially on a combination of hydrophobic interaction and of adsorption chromatography by the rapid fast protein liquid chromatographic technique. Applying the same method, a relative molecular mass of 9.1 . 10(6) daltons was obtained by gel filtration on Superose 6 HR 10/30 for the pyruvate dehydrogenase complex from T. aquaticus. The same column served to resolve the pyruvate dehydrogenase complex into its enzyme components.

Animals↗
PubMed1990

Comparative kinetics of D-xylose and D-glucose isomerase activities of the D-xylose isomerase from Thermus aquaticus HB8.

The D-xylose isomerase from T. aquaticus accepts, besides D-xylose, also D-glucose, and, with lower efficiency, D-ribose, and D-arabinose as alternative substrates. The activity of the enzyme is strictly dependent on divalent cations. Mn2+ is most effective in the D-xylose isomerase reaction and Co2+ in the D-glucose isomerization. Mg2+ is active in both reactions, Zn2+ only in the further one. The enzyme is strongly inhibited by Cu2+, and weakly by Ni2+, Fe2+, and Ca2+. A hyperbolic dependence of the reaction velocity of the D-xylose isomerase on the concentration of D-xylose xylose and of D-glucose was found, while biphasic saturation curves were obtained by variation of the metal ion concentrations. The D-glucose isomerization reaction shows normal behaviour with respect to the metal ions. A kinetic model was derived on the basis of the assumption of two binding sites for divalent cations, one cofactor site with higher affinity and a second, low affinity site, which modulates the activity of the enzyme.

Aldose-Ketose Isomerases↗
PubMed1989

Interaction between catalytic and regulatory sites of the pyruvate dehydrogenase from Escherichia coli studied by the ESR technique.

The accessibility of sulfhydryl groups at the pyruvate dehydrogenase component of the pyruvate dehydrogenase multienzyme complex from Escherichia coli was reinvestigated. Hydrophobic interactions appear to control the reactivity of an essential cysteine residue at the active site with thiol reagents. This explains why the essential cysteine residue reacts only with thiol reagents of minor polarity, like p-hydroxymercuribenzoate or phenylmercuric nitrate, but not with Ellman's reagent or jodoacetamide. The pyruvate dehydrogenase component was modified with a nitroxide derivative of p-hydroxymercuribenzoate. The ESR spectrum of the spin-labelled enzyme changed dramatically upon addition of the cofactors thiamine diphosphate and Mg2+. Obviously spin-spin interaction occurs under these conditions caused by a transition of an inactive to an active state of the enzyme. The same conformational change is observed when the allosteric activator AMP instead of the cofactors was bound to the enzyme. The implications of these results for the allosteric regulation of the pyruvate dehydrogenase complex are discussed.

Dithionitrobenzoic Acid↗