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Biomedical subjects

E Mertens

Publications and source records attributed to E Mertens.

13 recordsLinked to original sources
PubMed1992

Pyruvate kinase from Trichomonas vaginalis, an allosteric enzyme stimulated by ribose 5-phosphate and glycerate 3-phosphate.

Trichomonas vaginalis pyruvate kinase was purified over 1750 fold to a specific activity greater than 100 mumol min-1 (mg protein)-1. The enzyme is a tetramer of M(r) 266,000, consisting of subunits of M(r) 53,000 and 56,000 in equivalent amounts. Its activity was dependent on the presence of magnesium but was not stimulated by potassium or ammonium. The enzyme exhibited positive cooperativity towards phosphoenolpyruvate and was inhibited by inorganic phosphate, which increased the sigmoidicity of the saturation curve for phosphoenolpyruvate without affecting maximal activity. It was heterotropically stimulated by ribose 5-phosphate and glycerate 3-phosphate, not previously known to act on eukaryotic pyruvate kinases, but was unaffected by known effectors of most pyruvate kinases, including fructose 1,6-bisphosphate and fructose 2,6-bisphosphate.

Allosteric Regulation↗
PubMed1991

Pyrophosphate-dependent phosphofructokinase, an anaerobic glycolytic enzyme?

Recent evidence indicates that in as diverse organisms as unicellular eukaryotes, higher plants and prokaryotes, anaerobic glycolysis relies on a pyrophosphate-dependent phosphofructokinase instead of the classical ATP-dependent enzyme. This difference in phosphoryl donor specificity does not necessarily reflect a primitive metabolism, as thought earlier, but could rather be the result of convergent evolution, fostered by the energetic advantage conferred to the cell when glycolysis is the sole source of ATP.

Adenosine Triphosphate↗
PubMed1978

[Preoperative detection of a bleeding Meckel's diverticulum by 99mTc-pertechnetate scinitigraphy (author's transl)].

A Meckel's diverticulum containing gastric mucosa was causing recurrent intestinal bleeding in a 5-year old boy. 99mTc-pertechnetate scintigraphy was used to demonstrate the heterotopic gastric mucosa preoperatively. Compared to intestinal radiography and angiography, 99mTc-pertechnetate scintigraphy is a mild and uncomplicated investigation without any risk and with a minimum of radiation exposure. Evaluating its results critically this procedure can be of great help in the preoperative diagnosis of intestinal bleedings of unknown origin.

Age Factors↗
PubMed1975

[Experiences in the determination of thyroxine iodine in serum in various functional conditions of the thyroid gland].

A report is given on the method of the thyroxine iodine determination in the serum. Of 213 patients the result of the thyroxine iodine determination was compared with the clinically and radiologically established functional condition of the thyroid gland. The findings are discussed. Similar results were also reported of other in-vitro-tests (T3-test, T4-test, BEJ and PBJ). According to our experiences we consider the thyroxine iodine determination in the serum siutable as screening test which - when there is a suspicion of a hypo- or hyper- thyroidism - needs the supplementation by the radio-iodine functional and localisation tests.

Humans↗
PubMed1975

DNA-synthesis and DNA-methylation in the spleen of immunized mice.

Methylation of spleen DNA was investigated in mice immunized with bovine serum albumin. At the time of the highest incorporation of deoxythymidine into DNA -24 hours after antigen application--there is an elevated DNA methylation rate as shown by the transfer of the methyl group of methionine to DNA cytosine as well as by the conversion of DNA cytosine to DNA 5-methyl-cytosine. There is no difference in the methylation rate between bulk DNA and satellite DNA.

Adenine↗
PubMedDate not supplied

Glucokinase and fructokinase of Trichomonas vaginalis and Tritrichomonas foetus.

Trichomonas vaginalis and Tritrichomonas foetus contain glucokinase and not a hexokinase of broad hexose specificity. Tritrichomonas foetus also contains a specific fructokinase which could be resolved from glucokinase by anion exchange chromatography. Native T. vaginalis glucokinase had a Mr of 76,000, and SDS-PAG electrophoresis showed two equally stained bands corresponding to Mr 40,000 and 38,000. Glucose and ATP were by far the best substrates for both trichomonad glucokinases, with Km values as low as 33-35 microM and 75-83 microM, respectively. Substrate saturation curves for these enzymes were all hyperbolic. Tritrichomonas foetus fructokinase required fructose and ATP, with Km values of 200 microM and 81 microM. None of the activities was affected by a number of potential regulatory metabolites, including glucose-6-phosphate. The only exception was AMP which in supraphysiological concentrations had an inhibitory effect on T. foetus fructokinase. In conclusion, the absence of regulation at the hexose phosphorylation step described here, as well as the presence of an easily reversible PPi: fructose-6-phosphate 1-phosphotransferase described previously (Mertens, E., Van Schaftingen, E. & Müller, M. 1989. Mol. Biochem. Parasitol., 37:183-190), suggest that the rate of the 1st part of glycolysis in trichomonads is controlled only by the intracellular availability of hexoses.

Animals↗