Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.2 (PDK1)
 2,238 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The regulatory properties of the Ca2+-sensitive intramitochondrial enzymes (pyruvate dehydrogenase phosphate phosphatase, NAD+-isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase) in extracts of rat liver mitochondria appeared to be essentially similar to those described previously for other mammalian tissues. In particular, the enzymes were activated severalfold by Ca2+, with half-maximal effects at about 1 microM-Ca2+ (K0.5 value). In intact rat liver mitochondria incubated in a KCl-based medium containing 2-oxoglutarate and malate, the amount of active, non-phosphorylated, pyruvate dehydrogenase could be increased severalfold by increasing extramitochondrial [Ca2+], provided that some degree of inhibition of pyruvate dehydrogenase kinase (e.g. by pyruvate) was achieved. The rates of 14CO2 production from 2-oxo-[1-14C]glutarate at non-saturating, but not at saturating, concentrations of 2-oxoglutarate by the liver mitochondria (incubated without ADP) were similarly enhanced by increasing extramitochondrial [Ca2+]. The rates and extents of NAD(P)H formation in the liver mitochondria induced by non-saturating concentrations of 2-oxoglutarate, glutamate, threo-DS-isocitrate or citrate were also increased in a similar manner by Ca2+ under several different incubation conditions, including an apparent 'State 3.5' respiration condition. Ca2+ had no effect on NAD(P)H formation induced by beta-hydroxybutyrate or malate. In intact, fully coupled, rat liver mitochondria incubated with 10 mM-NaCl and 1 mM-MgCl2, the apparent K0.5 values for extramitochondrial Ca2+ were about 0.5 microM, and the effective concentrations were within the expected physiological range, 0.05-5 microM. In the absence of Na+, Mg2+ or both, the K0.5 values were about 400, 200 and 100 nM respectively. These effects of increasing extramitochondrial [Ca2+] were all inhibited by Ruthenium Red. When extramitochondrial [Ca2+] was increased above the effective ranges for the enzymes, a time-dependent deterioration of mitochondrial function and ATP content was observed. The implications of these results on the role of the Ca2+-transport system of the liver mitochondrial inner membrane are discussed.
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PMID:Characterization of the effects of Ca2+ on the intramitochondrial Ca2+-sensitive enzymes from rat liver and within intact rat liver mitochondria. 300 Mar 55

The activity of the pyruvate dehydrogenase kinase, which phosphorylates and thereby inactivates the pyruvate dehydrogenase complex, was stimulated by malonyl-CoA. Treatment with [2-14C]malonyl-CoA resulted in acylation of sites in the complex. Both acylation and activation of kinase activity increased in a time-dependent manner with a parallel increase in those activities when the malonyl-CoA:CoA ratio was varied. Protein-bound acyl groups were labilized by performic acid treatment indicating their attachment to protein at thiol residues; however, the product released was volatile, which is not characteristic of malonic acid. While malonyl-CoA was initially free of acetyl-CoA, stimulation of kinase activity and acylation of sites in the complex by malonyl-CoA were shown to be contingent upon enzyme-catalyzed decarboxylation. Decarboxylation appeared to be catalyzed by a trace contaminant present in highly purified preparations of both the pyruvate and 2-oxoglutarate dehydrogenase complexes. Under conditions in which both free CoA was removed (by conversion to succinyl-CoA) and then, after various periods, free acetyl-CoA was removed (by enzymic conversion to acetyl phosphate), both acetylation of sites in the complex and activation of kinase activity increased in a time-dependent manner. Concomitantly there was a decrease in the concentration dependence for activation of the kinase by malonyl-CoA. Our results strongly support the conclusion that activation of kinase activity is associated with acylation of sites in the complex, and that, in the case of malonyl-CoA, those processes depend on enzyme-catalyzed decarboxylation.
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PMID:Mechanism of activation of bovine kidney pyruvate dehydrogenase a kinase by malonyl-CoA and enzyme-catalyzed decarboxylation of malonyl-CoA. 401 76

Intramitochondrial substrate metabolism was examined in cultured neuroblastoma NB41A3 cells exposed to endotoxin in order to elucidate possible causes for the changes in [ATP]/[ADP][Pi] and [NAD+]/[NADH] reported by us previously in these cells [1]. Flux through pyruvate dehydrogenase (PDH), measured with [1-14C]-pyruvate, was inhibited by 54% within 10 min in endotoxin-treated cells (0.99 nmol/min/mg dry wt vs 0.46 nmol/min/mg dry wt). In contrast, flux through 2-oxoglutarate dehydrogenase, measured with [1-14C]-glutamate was unaltered (0.79 nmol/min/mg dry wt). Dichloroacetate, an inhibitor of PDH kinase, restored flux through PDH to control levels. In endotoxin-treated cells, only 44% of the total PDH complex was in the active (nonphosphorylated) form as compared to 72% in control cells. Equilibrium uptake studies with 45Ca2+ and atomic absorption measurements showed that intracellular [Ca2+] in endotoxin-treated cells was about 20% lower than in control cells. It is postulated that binding of endotoxin to the plasma membrane triggers a sequence of events that lead to an initial decline in intracellular calcium concentration and that this latter event may be responsible for the inhibition of PDH phosphatase and consequent conversion of the complex to its inactive phosphorylated form.
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PMID:Cellular effects of endotoxin in vitro. I. Effect of endotoxin on mitochondrial substrate metabolism and intracellular calcium. 635 31