scholarly journals Effect of pH on the inhibition of the nicotinamide–adenine dinucleotide-specific isocitrate dehydrogenase from baker's yeast by anions

1968 ◽  
Vol 109 (3) ◽  
pp. 361-368 ◽  
Author(s):  
C. Cennamo ◽  
G. Montecuccoli ◽  
G. Bonaretti ◽  
L. Razzoli
Keyword(s):  
Isocitrate Dehydrogenase ◽  
Nicotinamide Adenine Dinucleotide ◽  
Substrate Concentration ◽  
Ph Dependence ◽  
Chloride Concentration ◽  
Enzymic Activity ◽  
Baker’S Yeast ◽  
Nicotinamide Adenine ◽  
Baker's Yeast ◽  
Effect Of Ph

1. The sensitivity of the NAD+-specific isocitrate dehydrogenase from baker's yeast towards inhibition by anions decreases with decrease in pH. The patterns of the pH-dependence of the enzymic activity can be explained by this effect. 2. In the presence of a high isocitrate concentration, citrate, unlike AMP, has no antagonizing effect on the inhibition of the enzyme by anions. In the presence of AMP, citrate inhibits the enzyme at high isocitrate concentration and activates at low isocitrate concentration. 3. The effects on the enzymic activity of the previous incubation of the enzyme were studied in relation to the substrate concentration, the chloride concentration and the presence of citrate and AMP.

scholarly journals The effect of pH on the characteristics of the binding of nicotinamide–adenine dinucleotide by nicotinamide–adenine dinucleotide specific isocitrate dehydrogenase from pea mitochondria

1970 ◽  
Vol 116 (5) ◽  
pp. 819-824 ◽  
Author(s):  
G. F. Cox ◽  
D. D. Davies
Keyword(s):  
Isocitrate Dehydrogenase ◽  
Nicotinamide Adenine Dinucleotide ◽  
Maximum Velocity ◽  
Nicotinamide Adenine ◽  
Half Maximum ◽  
Ph Optimum ◽  
Effect Of Ph ◽  
Ph Values ◽  
Metabolic Significance

1. The effect of pH on the Vmax. and concentration of NAD+ at half-maximum velocity at a constant isocitrate concentration was examined, and the results were related to the requirements for binding of H+ ions to the enzyme. 2. The effect of varying the NAD+ concentration on the pH optimum with constant isocitrate concentration was studied. 3. A comparison has been made between the effect of isocitrate concentration on the characteristics of binding of NAD+ and the effect of NAD+ concentration on the characteristics of isocitrate binding at three different pH values. 4. The mechanistic and metabolic significance of these studies is considered.

scholarly journals The effects of pH and citrate on the activity of nicotinamide–adenine dinucleotide-specific isocitrate dehydrogenase from pea mitochondria

1969 ◽  
Vol 113 (5) ◽  
pp. 813-820 ◽  
Author(s):  
G. F. Cox ◽  
D. D. Davies
Keyword(s):  
Density Gradient ◽  
Isocitrate Dehydrogenase ◽  
Nicotinamide Adenine Dinucleotide ◽  
Substrate Concentration ◽  
Density Gradient Centrifugation ◽  
Gradient Centrifugation ◽  
Nicotinamide Adenine ◽  
Ph Optimum ◽  
Effects Of Ph ◽  
Metabolic Significance

1. The effect of pH on the co-operative activation of the NAD-specific isocitrate dehydrogenase from pea mitochondria by isocitrate is shown. 2. The interlinked effects of pH on the affinity of the NAD-specific isocitrate dehydrogenase for isocitrate and the dependence of the pH optimum on the substrate concentration are presented. 3. A consideration of the conditions of pH and substrate concentration under which citrate activates the NAD-specific isocitrate dehydrogenase demonstrates similarities between the binding of isocitrate and citrate. 4. A comparison of the effects of citrate and pH on the gross structure of the enzyme is investigated by density-gradient centrifugation. 5. The kinetic interpretations of these results are briefly considered. 6. The metabolic significance of these studies is discussed.

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