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Biomedical subjects

R Silverstein

Publications and source records attributed to R Silverstein.

51 records · Page 3Linked to original sources
PubMed1980

Evidence for an essential hydrophobic domain in the maintenance of phosphoenolpyruvate carboxykinase activity. Site-specific binding and inactivation by 1-anilinonaphthalene-8-sulfonate.

1-Anilinonaphthalene-8-sulfonate (ANS) binds to phosphoenolpyruvate carboxykinase with subsequent rapid inactivation. Kinetics are saturating, with an enzyme half-life of 0.29 min at 4 x 10(-4) M ANS. IDP, GDP, and phosphoenolpyruvate protect against the inactivation. The enzyme is not covalently modified and it retains an affinity for protecting substrates and substrate analogs, with the exception of oxalate. Binding of ANS occurs in a hydrophobic environment, as suggested by the changes in fluorescence emission, and is markedly pH-dependent, leading to more rapid inactivation at acid pH. Inactivation by ANS differs in this respect from inactivation by N-(iodoacetylaminoethyl)-5-naphthylamine-1-sulfonate which affinity labels the enzyme (Silverstein, R., Rawitch, A.B., and Grainger, D.A. (1979) Biochem. Biophys. Res Commun. 87, 911-918). Though the mechanism by which ANS inactivates the enzyme is unclear, the effect is atypical in that ANS binding does not normally lead to irreversible inactivation.

Anilino Naphthalenesulfonates↗
PubMed1978

Iatrogenic arteriovenous fistula. An unusual complication of indwelling pericardial catheter and intrapericardial steroid instillation for the treatment of uremic pericarditis.

The drainage and instillation of poorly absorbable corticosteroids has recently been suggested as an laternative to the present modes of therapy for uremic pericarditis. One patient who underwent such a therapeutic approach subsequently had a left internal mammary artery to right internal mammary vein arteriovenous fistula develop. To our knowledge, this is the first report of the development of arteriovenous fistula after either pericardiocentesis or intrapericardial instillation of steroids.

Adult↗
PubMed1978

Purification of hepatic phosphoenolpyruvate carboxykinase by affinity and hydrophobic chromatography.

Phosphoenolpyruvate carboxykinase has been purified by a procedure involving chromatography on norleucine-Sepharose, using a decreasing (NH4)2 SO4-inorganic phosphate concentration gradient, followed by chromatography on GMP-Sepharose. The enzyme is eluted from the affinity column with 2.5 X 10(-5)m IDP. The same procedure is applicable to hog mitochondrial and cytosol enzymes yielding the enzyme as a single band on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The corresponding molecular weight is 65,000 for each enzyme. Discontinuous polyacrylamide gel electrophoresis of the mitochondrial enzyme gave two sharp bands that were found to contain carboxykinase activity upon assay of gel slices. Similar analysis of the cytosol enzyme showed a much different staining pattern and four regions of carboxykinase activity. Plots of relative mobility of the two mitochondrial bands vs. per cent polyacrylamide in the gels gave parallel lines, confirming that the two bands did not result from enzyme aggregation. Elution of the enzyme upon analytical Sephacryl S-200 chromatography did, however, produce some resolution of the two bands without change in specific activity. The purification procedure described above has been applied also to the human mitochondrial enzyme with similar results. The molecular weight, similarly is 68,000.

Animals↗
PubMedDate not supplied

Effect of hydrazine sulfate on glucose-regulating enzymes in the normal and cancerous rat.

Glucokinase, hexokinase, fructose 1,6-bisphosphatase and phosphoenolpyruvate carboxykinase specific activities were monitored in liver cytosol from rats that had been made cancerous with 1,2-dimethylhydrazine and then treated with hydrazine sulfate. The presence of intestinal cancer, specifically, was confirmed by laparotomy and by histological analysis. Sustained changes in hexokinase and glucokinase specific activities were first evident during the latter weeks that the carcinogen was being administered. Upon subsequent treatment with hydrazine sulfate, glucokinase activity further decreased, and liver cytosolic phosphoenolpyruvate carboxykinase activity increased. Liver cytosolic hexokinase and fructose 1,6-bisphosphatase specific activities were not appreciably affected by the hydrazine sulfate treatment. These results indicate that hydrazine sulfate may influence carbohydrate metabolism at the level of selected liver enzymes not only with respect to gluconeogenesis, but also in terms of glucose uptake.

1,2-Dimethylhydrazine↗