Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.3.1.21 (CPT)
4,580 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mouse L929 cells were used to study the mechanism of cAMP induction of alkaline phosphatase (AP) activity. Following treatment with 200 microM 8-chlorophenylthio-cAMP (CPT-cAMP), alkaline phosphatase enzyme activity was observed to increase 80-fold after 24 h. The CPT-cAMP dose response of the alkaline phosphatase enzyme activity correlated well with the CPT-cAMP activation of cAMP-dependent protein kinase in L cells. A cDNA clone for the alkaline phosphatase was isolated and used to demonstrate a 10-fold increase in alkaline phosphatase mRNA levels after a 24-h treatment of L cells with CPT-cAMP. Increased mRNA levels were first detected 4-6 h, after CPT-cAMP treatment, and the level of alkaline phosphatase mRNA decreased rapidly after removal of CPT-cAMP. In vitro nuclear transcription studies showed that a 3-fold increase in alkaline phosphatase gene transcription was detectable 6 h after CPT treatment, and this increase was blocked by cycloheximide. In order to determine if the catalytic (C) subunit of cAMP-dependent protein kinase was able to mediate the induction of AP, L cells were transfected with expression vectors containing the metallothionein promoter and coding for the C alpha isoform of the catalytic subunit of cAMP-dependent protein kinase or for a catalytic subunit in which lysine 72 had been mutated to methionine (C alpha K72M). Zinc treatment of stably transfected cells expressing the wild-type C subunit showed an increase in protein kinase activity and an increase in AP activity. Zinc treatment of cells containing the mutant C subunit expression vector produced an increase in the amount of a protein which was recognized by C subunit antibodies on Western blots, but these cells showed no increase in protein kinase activity or in AP activity. We conclude that the C subunit is sufficient for transcriptional induction of the AP gene and that the phosphotransferase activity of the C subunit is required for this induction.
...
PMID:Induction of alkaline phosphatase in mouse L cells by overexpression of the catalytic subunit of cAMP-dependent protein kinase. 216 96

The carnitine acyltransferases which catalyse the reversible transfer of fatty acyl groups between carnitine and coenzyme A have been proposed to contain a catalytic histidine. Here, the chemical reactivity of active site groups has been used to demonstrate differences between the active sites of beef liver carnitine octanoyltransferase (COT) and carnitine palmitoyltransferase-II (CPT-II). Treatment of CPT-II with the histidine-selective reagent, diethyl pyrocarbonate (DEPC), resulted in simple linear pseudo-first-order kinetics. The reversal of the inhibition by hydroxylamine and the pKa (7.1) of the modified residue indicated that the residue was a histidine. The order of the inactivation kinetics showed that 1mol of histidine was modified per mol of CPT-II. When COT was treated with DEPC the kinetics of inhibition were biphasic with an initial rapid loss of activity followed by a slower loss of activity. The residue reacting in the faster phase of inhibition was not a histidine but possibly a serine. The modification of this residue did not lead to complete loss of activity suggesting that a direct role in catalysis is unlikely. It was deduced that the residue modified by DEPC in the slower phase was a lysine and indeed fluorodinitrobenzene (FDNB) inactivated COT with linear pseudo-first-order kinetics. The COT peptide containing the FDNB-labelled lysine was isolated and sequenced. Alignment of this sequence placed it 10 amino acids downstream of the putative active-site histidine.
...
PMID:Active sites residues of beef liver carnitine octanoyltransferase (COT) and carnitine palmitoyltransferase (CPT-II). 948 Sep 26

Our earlier work using intact mitochondria and isolated mitochondrial outer membranes confirms the observations of Murthy and Pande that CPT-I is located on the mitochondrial outer membranes and supports the notion that this enzyme has a malonyl-CoA binding domain facing the cytosol and an acyl-CoA binding domain facing the inter membrane space. Our data also suggests that coenzyme A binds at the active site of CPT-I, as does acyl-CoA, 2-bromopalmitoyl-CoA, and (+)-hemipalmitoylcarnitinium, but malonyl-CoA does not bind at that site. Inhibition of CPT-I at the malonyl-CoA binding site by HPG and Ro 25-0187, which have no CoA moiety, contributes to a resolution of this question in that the CoA itself is not essential for the binding of malonyl-CoA to its regulatory site, but the dicarbonyl function which is present in malonyl-CoA, HPG, and Ro 25-0187 is absolutely essential. Our re-evaluation of the topology of hepatic mitochondrial CPT-I confirms the original observations that this enzyme has at least two different binding domains, one domain binding malonyl-CoA, HPG, and Ro-25-187 and the other domain binding acyl-CoA and other inhibitors of CPT-I. Furthermore, the malonyl-CoA binding domain is exposed to the cytosolic face of the membrane. Our data showing that treatment of the intact mitochondria with trypsin causes release of adenylate kinase which indicates that trypsin has damaged the mitochondrial outer membrane, possibly allowing trypsin to enter the intermembrane space and act on CPT from within the outer membrane. Since trypsin's action is limited to arginine and lysine residues, an alternative explanation could be that the portion of the protein domain responsible for malonyl-CoA inhibition may not contain these residues. The latter explanation is plausible, since malonyl-CoA was able to protect against loss of activity and sensitivity to inhibition, but did not protect against loss of adenylate kinase, suggesting that rupture of the outer membrane is not necessarily related to loss of CPT activity. These results suggest that some protein domain that is necessary for CPT activity is exposed on the outer surface of the outer membranes. Therefore, it seems likely that trypsin would have to be able to hydrolyse protein domains of CPT that are inaccessible to Nagarse and papain.
...
PMID:Topology of hepatic mitochondrial carnitine palmitoyltransferase I. 1070 25

We have identified a novel missense mutation in the carnitine palmitoyltransferase II (CPT II) gene in a child with CPT II deficiency characterized clinically by episodes of myalgia and myoglobinuria induced by intercurrent febrile illnesses. The patient was heterozygous for a G-to-A substitution at codon 487, changing an encoded glutamic acid to a lysine (E489K), while the other allele carried the common S113L mutation. This case enlarges the spectrum of mutations in patients with CPT II deficiency, and confirms the association of the S113L mutation with the muscular form.
...
PMID:Novel mutation in the CPT II gene in a child with periodic febrile myalgia and myoglobinuria. 1086 82

A component of isoprenaline-mediated vasorelaxation in pulmonary arteries is mediated by nitric oxide (NO). We examined the effects of physiological concentrations (</=400 microM) of L-arginine on isoprenaline-induced relaxation in rat pulmonary arteries, and following inhibition of L-arginine uptake with L-lysine. In addition, we examined the role of the endothelium, and whether L-arginine affected acetylcholine (ACh)-induced relaxation. Isoprenaline-induced relaxation was potentiated by 400 microM L-arginine in pulmonary arteries; maximum relaxation was increased from 83+/-4% of initial tone to 94+/-4% (P<0.05). L-lysine (10 mM) not only abolished the potentiation by L-arginine, but suppressed relaxation compared to control (70+/-4%, P<0.05), even in the absence of L-arginine added to the bath. Blockade of NO synthase with 100 microM L-NMMA or removal of the endothelium inhibited isoprenaline-induced relaxation to the same extent as L-lysine, and under these conditions the presence or absence of 400 microM L-arginine made no difference. L-lysine had no additional effect when applied in combination with L-NMMA. The effect of extracellular L-arginine was concentration dependent, with an apparent EC(50) of approximately 1-7 microM. Relaxation to the membrane permeant cyclic AMP analogue CPT cyclic AMP was also potentiated by L-arginine and inhibited by L-lysine. There was however no difference in relaxation induced by acetylcholine (ACh) in the presence of L-arginine or L-lysine, and isoprenaline-induced relaxation of mesenteric arteries was unaffected by L-arginine or L-lysine. These results strongly suggest that extracellular L-arginine is critically important for development of the NO- and endothelium-dependent component of cyclic AMP-induced vasorelaxation in rat pulmonary arteries, but is not required for ACh-induced relaxation. As the apparent EC(50) for this effect is in the low micromolar range it is likely to be fully activated in vivo, as plasma L-arginine is >150 microM.
...
PMID:Critical dependence of the NO-mediated component of cyclic AMP-induced vasorelaxation on extracellular L-arginine in pulmonary arteries of the rat. 1088 83

1. The NO-dependent component of cyclic AMP-induced vasorelaxation in rat pulmonary arteries is critically dependent on extracellular L-arginine but independent of endothelial cell intracellular [Ca(2+)]. We examined whether L-arginine uptake was also essential for NO production induced by passive stretch or isometric tension, processes also reported to be Ca(2+)-independent. 2. The passive length-tension curve was depressed by physiological concentrations of L-arginine (400 microM; P<0.05). Inhibition of the y(+) transporter with 10 mM L-lysine, NO synthase with L-NAME (100 microM), or protein tyrosine kinase with erbstatin A (30 microM) caused identical upward shifts (P<0.001), alone or in combination. Tyrphostin 23 was similar to erbstatin A, whilst the inactive analogue tyrphostin A1 and genistein were without effect. 3. L-arginine (400 microM) shifted the PGF(2 alpha) concentration-response curve under isometric conditions to the right (P<0.05), whereas L-NAME or L-lysine caused a leftward shift (P<0.001). Tyrphostin 23 (30 microM) more than reversed the L-arginine-induced suppression of PGF(2 alpha)-induced tension; subsequent addition of L-NAME had no effect. The L-lysine-sensitive component of CPT cyclic AMP-induced vasorelaxation was abolished by erbstatin A. 4. ACh-induced vasorelaxation was approximately 80% inhibited by L-NAME, but was not affected by L-lysine or 400 microM L-arginine. Erbstatin A reduced the vasorelaxation by only approximately 25%. 5. We conclude that activation of NO production by stretch, isometric tension, or cyclic AMP in rat pulmonary arteries is critically dependent on the presence and uptake of physiological concentrations of extracellular L-arginine, and protein tyrosine kinase activity. This directly contrasts with ACh-induced vasorelaxation, which was independent of extracellular L-arginine, and relatively unaffected by tyrosine kinase inhibition.
...
PMID:Essential role of L-arginine uptake and protein tyrosine kinase activity for NO-dependent vasorelaxation induced by stretch, isometric tension and cyclic AMP in rat pulmonary arteries. 1109 Jan 23

Mammalian mitochondrial membranes express two active but distinct carnitine palmitoyltransferases: carnitine palmitoyltransferase I (CPTI), which is malonyl coA-sensitive and detergent-labile; and carnitine palmitoyltransferase II (CPTII), which is malonyl coA-insensitive and detergent-stable. To determine the role of the highly conserved C-terminal acidic residues glutamate 487 (Glu(487)) and glutamate 500 (Glu(500)) on catalytic activity in rat liver CPTII, we separately mutated these residues to alanine, aspartate, or lysine, and the effect of the mutations on CPTII activity was determined in the Escherichia coli-expressed mutants. Substitution of Glu(487) with alanine, aspartate, or lysine resulted in almost complete loss in CPTII activity. Because a conservative substitution mutation of this residue, Glu(487) with aspartate (E487D), resulted in a 97% loss in activity, we predicted that Glu(487) would be at the active-site pocket of CPTII. The substantial loss in CPTII activity observed with the E487K mutant, along with the previously reported loss in activity observed in a child with a CPTII deficiency disease, establishes that Glu(487) is crucial for maintaining the configuration of the liver isoform of the CPTII active site. Substitution of the conserved Glu(500) in CPTII with alanine or aspartate reduced the V(max) for both substrates, suggesting that Glu(500) may be important in stabilization of the enzyme-substrate complex. A conservative substitution of Glu(500) to aspartate resulted in a significant decrease in the V(max) for the substrates. Thus, Glu(500) may play a role in substrate binding and catalysis. Our site-directed mutagenesis studies demonstrate that Glu(487) in the liver isoform of CPTII is essential for catalysis.
...
PMID:Identification by mutagenesis of a conserved glutamate (Glu487) residue important for catalytic activity in rat liver carnitine palmitoyltransferase II. 1220 Apr 19

The identification of post-translational modifications is difficult especially for hydrophobic membrane proteins. Here we present the identification of several types of protein modifications on membrane proteins isolated from mitochondrial outer membranes. We show, in vivo, that the mature rat liver mitochondrial carnitine palmitoyltransferase-I enzyme is N-terminally acetylated, phosphorylated on two threonine residues, and nitrated on two tyrosine residues. We show that long chain acyl-CoA synthetase 1 is acetylated at both the N-terminal end and at a lysine residue and tyrosine residues are found to be phosphorylated and nitrated. For the three voltage-dependent anion channel isoforms present in the mitochondria, the N-terminal regions of the protein were determined and sites of phosphorylation were identified. These novel findings raise questions about regulatory aspects of carnitine palmitoyltransferase-I, long chain acyl-CoA synthetase and voltage dependent anion channel and further studies should advance our understanding about regulation of mitochondrial fatty acid oxidation in general and these three proteins in specific.
...
PMID:Post-translational modifications of rat liver mitochondrial outer membrane proteins identified by mass spectrometry. 1747 30

Intracellular redox balance may affect nutrient metabolism in skeletal muscle. Astaxanthin, a carotenoid contained in various natural foods, exerts high antioxidative capacity in the skeletal muscles. The present study investigated the effect of astaxanthin on muscle lipid metabolism in exercise. ICR mice (8 weeks old) were divided into four different groups: sedentary, sedentary treated with astaxanthin, running exercise, and exercise treated with astaxanthin. After 4 weeks of treatment, exercise groups performed treadmill running. Astaxanthin increased fat utilization during exercise compared with mice on a normal diet with prolongation of the running time to exhaustion. Colocalization of fatty acid translocase with carnitine palmitoyltransferase I (CPT I) in skeletal muscle was increased by astaxanthin. We also found that hexanoyl-lysine modification of CPT I was increased by exercise, while astaxanthin prevented this increase. In additional experiment, we found that astaxanthin treatment accelerated the decrease of body fat accumulation with exercise training. Our results suggested that astaxanthin promoted lipid metabolism rather than glucose utilization during exercise via CPT I activation, which led to improvement of endurance and efficient reduction of adipose tissue with training.
...
PMID:Astaxanthin improves muscle lipid metabolism in exercise via inhibitory effect of oxidative CPT I modification. 1808 22

SUMO is a ubiquitin-like protein that is post-translationally attached to one or more lysine residues on target proteins. Despite having only 18% sequence identity with ubiquitin, SUMO contains the conserved betabetaalphabetabetaalphabeta fold present in ubiquitin. However, SUMO differs from ubiquitin in having an extended N-terminus. In S. pombe the N-terminus of SUMO/Pmt3 is significantly longer than those of SUMO in S. cerevisiae, human and Drosophila. Here we investigate the role of this N-terminal region. We have used two dimensional gel electrophoresis to demonstrate that S. pombe SUMO/Pmt3 is phosphorylated, and that this occurs on serine residues at the extreme N-terminus of the protein. Mutation of these residues (in pmt3-1) results in a dramatic reduction in both the levels of high Mr SUMO-containing species and of total SUMO/Pmt3, indicating that phosphorylation of SUMO/Pmt3 is required for its stability. Despite the significant reduction in high Mr SUMO-containing species, pmt3-1 cells do not display an aberrant cell morphology or sensitivity to genotoxins or stress. Additionally, we demonstrate that two lysine residues in the N-terminus of S. pombe SUMO/Pmt3 (K14 and K30) can act as acceptor sites for SUMO chain formation in vitro. Inability to form SUMO chains results in aberrant cell and nuclear morphologies, including stretched and fragmented chromatin. SUMO chain mutants are sensitive to the DNA synthesis inhibitor, hydroxyurea (HU), but not to other genotoxins, such as UV, MMS or CPT. This implies a role for SUMO chains in the response to replication arrest in S. pombe.
...
PMID:SUMO chain formation is required for response to replication arrest in S. pombe. 1970


1 2 Next >>

---