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Biomedical subjects

E Hofmann

Publications and source records attributed to E Hofmann.

At least 253 records · Page 14Linked to original sources
PubMed1975

Reaction of yeast phosphofructokinase with succinic and maleic anhydride.

Modification of yeast phosphofructokinase by succinic and maleic anhydride influences the catalytic activity and the allosteric behaviour of the enzyme. Depending on the degree of succinylation and maleinylation a decrease of maximum activity, an increase of the apparent affinity for fructose-6-phosphate, a decrease of the Hill-coefficient and a diminution of ATP-inhibition are observed. Up to about 40% of the lysyl residues could be succinylated without dissociation of the hexameric protein, however with a decrease of the enzyme activity. More extensive succinylation or maleinylation causes a dissociation into subunits. The sedimentation coefficient is lowered from 20 S to about 3 S. The molecular weight of the smallest dissociation product was determined to 50 000 (+/- 10 000) by the sedimentation equilibrium method. The number of bound succinyl groups, as determined from radioactivity incorporation, exceeds the content of lysyl groups of the enzyme, indicating that the modifying reagent is also reacting with other amino acid residues.

Anhydrides↗
PubMed1975

Specific binding of Cibacron blue F3G-A to yeast phosphofructokinase.

The complex formation between the ATP-analogous reactive dye Cibacron blue F3G-A and yeast phosphofructokinase is accompanied by a red shift of the visible absorption spectrum. From the position of lambdamax of the dye-phosphofructokinase complex in the polarity scales obtained from model solvents it may be concluded that the chromophoric system is evidently located in a highly apolaric range of the enzyme protein. The spectrophotometric titration of yeast phosphofructokinase with Cibacron blue F3G-A yielded a sigmoidal binding curve, which can be described by the MONOD-WYMAN-CHANGEUX model.

Adenosine Triphosphate↗
PubMed1975

Affinity elution of pyruvate kinase from phosphocellulose.

Pyruvate kinase from ascites tumour cells can be eluted from phosphocellulose by very low concentrations of phosphoenolpyruvate, fructose 1,6-bisphosphate, adenosine 5'-diphosphate and pyrophosphate, respectively. The appropriate limiting conditions for "facilitated desorption" of the enzyme from phosphocellulose by these ligands have been elaborated for achieving maximum selectivity and recovery in the process of its purification. This method has been designated as "affinity elution chromatography" owing to the specific interactions between a ligand as a constituent of the eluting medium with the adsorbed enzyme, which causes its selective desorption from the ion-exchanger. Affinity elution with phosphoenolpyruvate has been found to be very effective for preparation of the M-types of pyruvate kinase. A specific activity of 420 for an almost homogeneous preparation of pyruvate kinase from ascites tumour cells has maximally been obtained.

Animals↗
PubMed1975

[Microcalorimetric determination of thermochemical parameters of the phosphofructokinase reaction].

A calorimetric procedure for determining deltaH, deltaG, deltaS and Keq of a bimolecular reaction with two or more products is described. By using this method the thermodynamic parameters of the phosphofructokinase reaction are determined. At pH 7.0 and 25 degrees C a reaction enthalpy of-6.96kcal/mole was found after correction for the neutralization enthalpy of the buffer and of the enthalpy difference of the magnesium complexes of ATP and ADP, respectively. The free energy of the phosphofructokinase reaction has been found under these conditions to be -3.96kcal/mole.

Adenosine Diphosphate↗