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Biomedical subjects

A Wendel

Publications and source records attributed to A Wendel.

175 records · Page 10Linked to original sources
PubMed1975

[Assay and normal levels of L-glutamate-L-cysteine-gamma-ligase (E.C. 6.3.2.2) in human erythrocytes; biosynthesis of glutathione V].

For the determination of the activity of glutamate: cysteine-gamma-ligase one method was optimized and a new micromethod was developed: a) Utilizing [14C] glutamate and cysteine as substrates, the product [14C] gamma-glutamylcysteine was isolated as its cadmium mercaptide and determined by liquid scintillation counting gamma-glutamyl-[14C] aminobutyrate, which was synthesized from glutamate and [14C] alpha-aminobutyrate was separated from remaining radioactive substrate by paper electrophoresis and counted. Both methods were used to determine the activity of the enzyme in human red blood cells. For 20 parallel determinations a standard deviation of +/- 9% and +/- 5% was obtained for method a and b, respectively. The specific activity of the enzyme in erythrocytes of adults was found to be 0.40 +/- 0.05 U/g hemoglobin with method a, and 0.50 +/- 0.05 U/g hemoglobin with method b.

Adenosine Triphosphate↗
PubMed1975

[Biosynthesis of glutathione. VI. Ocurrence and level of gamma-glutamylcysteine in human red cells (author's transl)].

The concentration of the glutathione precursor gamma-glutamylcysteine in hemolysates of human red cells was determined using three different methods. a) The [14C]N-ethylmaleimide derivatives of the intracellular sulfhydryl compounds were separated on a cation exchange column. The amount of [14C]N-ethylmaleimide glutamycysteine was radiochemically determined. b) With purified glutathione synthetase, an enzymatic endpoint metabolite determination was performed with [14C]glycine as one substrate. The amount of labelled glutathione formed from the gamma-glutamylcysteine present was measured radiochemically.

Cysteine↗
PubMed1975

[15-Hydroxyprostaglandin dehydrogenase from human placenta, II. Steady state kinetics and influence of prostaglandin F2alpha analogues (author's transl)].

A complete initial rate analysis of the forward reaction catalyzed by 15-hydroxyprostaglandin dehydrogenase from human term placenta was carried out at pH 7.4 (100mM triethanolamine) with the substrates NAD, and the prostaglandins E1, E2 and F2alpha. The limiting Michaelis constants, the dissociation constants, and the limiting maximum velocities for these substrates were calculated by fitting the obtained data by weighted linear regression analysis to the complete rate equation. The product inhibition of the reaction by NADH and 15-oxoprostaglandin was studied and the inhibition constants were graphically determined. The initial rate and inhibition patterns obtained indicate that the reaction follows kinetically an ordered Bi Bi mechanism. The prostaglandin F2alpha analogues ICI 81,008 and ICI 79,939 were not utilized by the enzyme. With ICI 81,008 a slight inhibition of the enzymatic reaction with prostaglandin F2alpha was observed, whereas ICI 79,939 showed no effect. The results are discussed with respect to their possible biological significance.

Alcohol Oxidoreductases↗
PubMed1975

[15-Hydroxyprostaglandin dehydrogenase from human placenta. 1. Isolation and characterization].

15-Hydroxyprostaglandin dehydrogenase was isolated from human term placenta up to a final purification of 380-fold. A spec. act. of 2000 mU/mg of protein was reached. The preparation was not homogeneous as judged by analytical disc electrophoresis. The enzyme could be stored in the presence of 50% glycerol and 10mM 2-mercaptoethanol without any loss of activity for at least one year. A distinct single protein band stained after discontinuous polyacrylamide gel electrophoresis was shown by enzymatic activity staining to correspond to 15-hydroxyprostaglandin dehydrogenase activity. Thus no evidence for the exitstence of isoenzymes was obtained. The protein in the final preparation steps showed neither alcohol dehydrogenase, NAD reductase, nor NADH oxidase activity, nor enzymatic conversion of prostaglandin or 15-oxoprostaglandin in the absence of NAD and NADH. No spontaneous reactions between NAD and prostaglandin or NADH and 15-oxoprostaglandin were detectable in the absence of the enzyme. Ethanol and glycerol slightly inhibited the reaction. Various buffers (Tris/HC1, potassium phosphate, HEPES, and triethanolamine) and salts (ammonium chloride, ammonium sulfate, potassium chloride, and sodium chloride) had different effects on the reaction rate. The pH profile of the reaction shows a plateau between pH 7.0 and 7.8 and a steep maximum at pH 9.5. A linear Arrhenius plot was obtained for the temperature dependence of the reaction from 20 to 37 degrees C. The molar activation enthalpy of the reaction was calculated to be 13.1 kcal/mole. The molecular weight of 15-hydroxyprostaglandin dehydrogenase was estimated to be 32000 -/+ 3000 by gel filtration on Sephadex G-150 in the presence of 10mM mercaptoethanol.

Alcohol Oxidoreductases↗
PubMedDate not supplied

The degradation of glutathione derivatives in the rat kidney.

Single proximal rat kidney tubules and Henle loops were microperfused with labelled S-substituted glutathione derivatives which are physiological mercapturic acid precursors. S-methyl-glutathione as well as the non-permeating bromo-sulfaleinglutathione adduct were degraded in the proximal convolution with a half-life of about 3.5 sec. The findings demonstrate that the brush-border membrane-bound renal gamma-glutamyl transpeptidase acts on luminal substrates and is involved in mercapturic acid synthesis and splitting of extracellular glutathione.

Animals↗