NADH inhibition

In studies with Isolated plant mitochondria, flavones, flava-nones, cinnamic acids, and benzoic acids were shown to Inhibit the oxidation of succinate, malate, and NADH Inhibition was... 

Isocitrate dehydrogenase is allosterically stimulated by ADP, which enhances the enzyme s affinity for substrates. The binding of isocitrate, NAD+, Mg2+, and ADP is mutually cooperative. In contrast, NADH inhibits iso-citrate dehydrogenase by directly displacing NAD+. ATP, too, is inhibitory. It is important to note that several steps in the cycle require NAD+ or FAD, which are abundant only when the energy charge is low. 

Note that ethanol consumption leads to an accumulation ofNADH. This high concentration of NADH inhibits gluconeogenesis by preventing the oxidation of lactate to pyruvate. In fact, the high concentration ofNADH will cause the reverse reaction to predominate, and lactate will accumulate. The consequences may be hypoglycemia and lactic acidosis. 

Both 7a//S-dehydroxylase and A -steroid reductase activities are stimulated by adding NAD to anaerobically dialyzed cell extracts of Eubacterium sp. V.P.I. 12708. NADH inhibited all 3 activities at high concentrations (0.5 mM) but stimulated 7a-dehydroxylase activity at lower concentrations (< 0.10 mM). Double reciprocal plots of NADH inhibition of 7a-dehydroxylase activity suggested negative cooper-ativity. The effect of low concentrations of NADH on the kinetics of 7/8-dehydroxyl-ase and A -steroid reductase activity is presently unknown. The activity of 7a-dehy-... 

The second regulatory site is the isocitrate dehydrogenase reaction. In this case, ADP and NAD+ are allosteric activators of the enzyme. We have called attention to the recurring pattern in which ATP and NADH inhibit enzymes of the pathway, and ADP and NAD+ activate these enzymes. 

NADH Inhibits isocitrate dehydrogenase and consec uently citrate accumulates... 

Pyruvate dehydrogenase a Multienzyme complex (see) responsible for the formation of acetyl-CoA from pyruvate, one of the central metabolic reactions (see Pyruvate, Acetyl-coenzyme A). It is subject to three types of control l.The enzyme complex is inhibited by acetyl-CoA and NADH the transace-tylase is inhibited by acetyl-CoA, and NADH inhibits the dihydrolipoyl dehydrogenase. These inhibitions are reversed by CoA and NAD, respectively. 2. Enzyme activity is influenced by the energy state of the cell the complex is inhibited by GTP and activated by AMP 3. The complex is inhibited when a specific serine residue in the pyruvate decarboxylase is phos-phorylated by ATP This phosphorylation is inhibited by pyruvate and ADP The complex is reactivated by... 

The reaction rate of NAD reduction in the reaction catalyzed by FDH can be described by double-substrate Michaelis-Menten equation with competitive NADH inhibition... 

---