Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The presence of high phosphoenolpyruvate carboxykinase (EC 4.1.1.32) activity in mouse islet cytosol has been demonstrated. The enzyme was activated by Mn2+ with a Ka of 100 X 10(-6) mol/l. The mean total activity of the Mn2+-stimulated phosphoenolpyruvate carboxykinase in islet cytosol estimated at 22 degrees C with saturating concentrations of the substrates oxaloacetate and ITP was 146 pmol/min per micrograms DNA. Km was calculated to be 6 X 10(-6) mol/l for oxaloacetate and 140 X 10(-6) mol/l for ITP. The islet phosphoenolpyruvate carboxykinase activity was not increased after starvation of the animals for 48 h. Preincubation of the cytosol at 4 degrees C with Fe2+, quinolinate, ATP, Pi, glucose 6-phosphate, fructose 1,6-bisphosphate, NAD+, NADH, oxaloacetate, ITP, cyclic AMP and Ca2+ had no effect on the enzyme activity. However, preincubation of the cytosol at 37 degrees C with ATP-Mg inhibited the Mn2+-stimulated phosphoenolpyruvate carboxykinase activity progressively with time and in a concentration-dependent manner. A similar but weaker inhibitory effect was observed with p[NH]ppA, whereas p[CH2]ppA, ADP, AMP, adenosine and Pi had no effect. It is tentatively suggested that ATP and p[NH]ppA either by adenylation or otherwise affect the interaction between islet phosphoenolpyruvate carboxykinase and the recently discovered Mr = 29000 protein modulator of the enzyme in such a way - perhaps by causing a dissociation between them - that phosphoenolpyruvate carboxykinase loses its sensitivity to Mn2+ activation.
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PMID:Phosphoenolpyruvate carboxykinase in mouse pancreatic islets. ATP-induced changes in sensitivity to Mn2+ activation. 638 41

The kdpFABC operon, which encodes the structural genes for the high affinity K+ transport complex KdpFABC, is regulated by the sensor kinase KdpD and the response regulator KdpE. KdpD is a bifunctional enzyme catalyzing the autophosphorylation by ATP and the dephosphorylation of the corresponding response regulator KdpE. Here, we demonstrate that the phosphatase activity of KdpD is dependent on ATP, whereas GTP, ITP, CTP, ADP, and GDP have no effect. The phosphatase activity requires only ATP binding, because nonhydrolyzable analogs (adenosine-5'-[gamma-thio]triphosphate and adenosine-5'-[beta,gamma-imido]triphosphate) work as well. However, KdpD proteins missing amino acids 12-128 are characterized by a phosphatase activity that is independent of ATP. These proteins are still able to respond to K+ starvation, but an increase in osmolarity is no longer sensed. Comparison of different KdpD sequences reveals a conserved motif in this amino acid region that is very similar to a classical ATP-binding site (Walker A motif). Replacement of the conserved Gly37, Lys38, and Thr39 residues in the consensus ATP-binding sequence results in a KdpD protein that causes a kdpFABC expression pattern comparable with that seen with KdpD proteins missing amino acids 12-128. However, in vitro phosphatase activity is comparable with that of wild-type KdpD. These results suggest that amino acids 12-128 of KdpD are important for its activity and that an additional ATP-binding site in the N-terminal region seems to be involved in modulation of the phosphatase activity.
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PMID:Truncation of amino acids 12-128 causes deregulation of the phosphatase activity of the sensor kinase KdpD of Escherichia coli. 965 26

Rel(Mtb) of Mycobacterium tuberculosis is responsible for the intracellular regulation of (p)ppGpp and the consequent ability of the organism to survive long-term starvation, indicating a possible role in the pathogenesis of tuberculosis. Purified Rel(Mtb) is a dual-function enzyme carrying out ATP: GTP/GDP/ITP 3'-pyrophosphoryltransferase and (p)ppGpp 3'-pyrophosphohydrolase reactions. Here we show that in the absence of biological regulators, Rel(Mtb) simultaneously catalyzes both transferase and hydrolysis at the maximal rate for each reaction, indicating the existence of two distinct active sites. The differential regulation of the opposing activities of Rel(Mtb) is dependent on the ratio of uncharged to charged tRNA and the association of Rel(Mtb) with a complex containing tRNA, ribosomes, and mRNA. A 20-fold increase in the k(cat) and a 4-fold decrease in K(ATP) and K(GTP) from basal levels for transferase activity occur when Rel(Mtb) binds to a complex containing uncharged tRNA, ribosomes, and mRNA (Rel(Mtb) activating complex or RAC). The k(cat) for hydrolysis, however, is reduced 2-fold and K(m) for pppGpp increased 2-fold from basal levels in the presence of the Rel(Mtb) activating complex. The addition of charged tRNA to this complex has the opposite effect by inhibiting transferase activity and activating hydrolysis activity. Differential control of Rel(Mtb) gives the Mtb ribosomal complex a new regulatory role in controlling cellular metabolism in response to stringent growth conditions that may be present in the dormant Mtb lesion.
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PMID:Differential regulation of opposing RelMtb activities by the aminoacylation state of a tRNA.ribosome.mRNA.RelMtb complex. 1099 31

The experiences of the 22 men from Ernest Shackleton's Endurance expedition of 1914-1916 who were marooned on Elephant Island during the Antarctic winter are not as well known as the narrative of the ship being beset and sunk, and Shackleton's open boat journey to South Georgia to rescue them. Frank Wild was left in charge of the marooned men by Shackleton and saved them from starvation and despair. The morale of the men in the face of extreme exposure to the elements, the ingenuity of their devices for survival and their diet, conversation and entertainments all reveal heroic qualities of Shackletonian endurance.
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PMID:Shackleton's men: life on Elephant Island. 1535 Jul 58