scholarly journals Effect of long-chain fatty acyl-CoA on mitochondrial and cytosolic ATP/ADP ratios in the intact liver cell

1984 ◽  
Vol 220 (2) ◽  
pp. 371-376 ◽  
Author(s):  
S Soboll ◽  
H J Seitz ◽  
H Sies ◽  
B Ziegler ◽  
R Scholz
Keyword(s):  
Liver Cell ◽  
Adenine Nucleotide ◽  
Intact Cell ◽  
Inhibitory Effect ◽  
Fatty Acyl ◽  
Fed State ◽  
Physiological Relevance ◽  
Chain Acyl ◽  
Long Chain

The effect of long-chain acyl-CoA on subcellular adenine nucleotide systems was studied in the intact liver cell. Long-chain acyl-CoA content was varied by varying the nutritional state (fed and starved states) or by addition of oleate. Starvation led to an increase in the mitochondrial and a decrease in the cytosolic ATP/ADP ratio in liver both in vivo and in the isolated perfused organ as compared with the fed state. The changes were reversed on re-feeding glucose in liver in vivo or on infusion of substrates (glucose, glycerol) in the perfused liver, respectively. Similar changes in mitochondrial and cytosolic ATP/ADP ratios occurred on addition of oleate, but, importantly, not with a short-chain fatty acid such as octanoate. It is concluded that long-chain acyl-CoA exerts an inhibitory effect on mitochondrial adenine nucleotide translocation in the intact cell, as was previously postulated in the literature from data obtained with isolated mitochondria. The physiological relevance with respect to pyruvate metabolism, i.e. regulation of pyruvate carboxylase and pyruvate dehydrogenase by the mitochondrial ATP/ADP ratio, is discussed.

scholarly journals Role of long-chain fatty acyl-CoA esters in the regulation of metabolism and in cell signalling

1997 ◽  
Vol 323 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Nils Joakim FÆRGEMAN ◽  
Jens KNUDSEN
Keyword(s):  
Binding Proteins ◽  
Feedback Inhibition ◽  
Fatty Acyl ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Release Channel ◽  
Δ9 Desaturase ◽  
Chain Acyl ◽  
Long Chain

The intracellular concentration of free unbound acyl-CoA esters is tightly controlled by feedback inhibition of the acyl-CoA synthetase and is buffered by specific acyl-CoA binding proteins. Excessive increases in the concentration are expected to be prevented by conversion into acylcarnitines or by hydrolysis by acyl-CoA hydrolases. Under normal physiological conditions the free cytosolic concentration of acyl-CoA esters will be in the low nanomolar range, and it is unlikely to exceed 200 nM under the most extreme conditions. The fact that acetyl-CoA carboxylase is active during fatty acid synthesis (Ki for acyl-CoA is 5 nM) indicates strongly that the free cytosolic acyl-CoA concentration is below 5 nM under these conditions. Only a limited number of the reported experiments on the effects of acyl-CoA on cellular functions and enzymes have been carried out at low physiological concentrations in the presence of the appropriate acyl-CoA-buffering binding proteins. Re-evaluation of many of the reported effects is therefore urgently required. However, the observations that the ryanodine-senstitive Ca2+-release channel is regulated by long-chain acyl-CoA esters in the presence of a molar excess of acyl-CoA binding protein and that acetyl-CoA carboxylase, the AMP kinase kinase and the Escherichia coli transcription factor FadR are affected by low nanomolar concentrations of acyl-CoA indicate that long-chain acyl-CoA esters can act as regulatory molecules in vivo. This view is further supported by the observation that fatty acids do not repress expression of acetyl-CoA carboxylase or Δ9-desaturase in yeast deficient in acyl-CoA synthetase.

scholarly journals Demonstration and characterization of phosphate transport in mammalian peroxisomes

2005 ◽  
Vol 389 (3) ◽  
pp. 717-722 ◽  
Author(s):  
Wouter F. Visser ◽  
Carlo W. van Roermund ◽  
Lodewijk Ijlst ◽  
Klaas J. Hellingwerf ◽  
Ronald J. A. Wanders ◽  
...  
Keyword(s):  
Small Molecules ◽  
Adenine Nucleotide ◽  
Phosphate Transport ◽  
Significant Extent ◽  
Peroxisomal Membrane ◽  
Chain Acyl ◽  
Long Chain

It is now well established that the peroxisomal membrane is not freely permeable to small molecules in vivo, which implies the existence of metabolite transporters in the peroxisomal membrane. A few putative peroxisomal metabolite transporters have indeed been identified, but the function of these proteins has remained largely unresolved so far. The only peroxisomal transporter characterized to a significant extent is the adenine nucleotide transporter, which is presumably required to sustain the activity of the intraperoxisomal very-long-chain-acyl-CoA synthetase. In addition to AMP, this acyl-CoA synthetase also produces pyrophosphate, which must be exported from the peroxisome. In the present study, we demonstrate that the peroxisomal membrane contains a transporter activity that facilitates the passage of phosphate and possibly pyrophosphate across the peroxisomal membrane. By reconstitution of peroxisomal membrane proteins in proteoliposomes, some kinetic parameters of the transporter could be established in vitro. The transporter can be distinguished from the mitochondrial phosphate transporter by its different sensitivity to inhibitors.

scholarly journals Importance of albumin binding in the assay for carnitine palmitoyltransferase

1983 ◽  
Vol 216 (2) ◽  
pp. 495-498 ◽  
Author(s):  
K McCormick ◽  
V J Notar-Francesco
Keyword(s):  
Enzyme Activity ◽  
Carnitine Palmitoyltransferase ◽  
Albumin Binding ◽  
Biochemical Modification ◽  
Physiological Relevance ◽  
Chain Acyl ◽  
Absolute Quantity ◽  
Substrate Concentrations ◽  
Long Chain ◽  
Do So

Alterations in the long-chain acyl-CoA binding to albumin in the carnitine palmitoyltransferase (CPT) assay appreciably affect the reaction at commonly used substrate concentrations. Since in the CPT assay the latter are typically well below saturation or Vmax. values, the measured enzyme activity depends on both the absolute quantity of albumin in the CPT assay and any biochemical modification of its binding. The present study verifies the striking dependence of the K0.5 for palmitoyl-CoA on albumin and the misleading ‘activation’ of the enzyme by compounds that also avidly bind to albumin. In assessing the intracellular physiological relevance of any modifier of CPT, the effects of protein binding in the assay assume particular importance. Indeed, any compound that alters CPT activity may do so, not directly, but as an assay artifact changing the free or unbound substrate concentrations.

Substrate preferences of long-chain acyl-CoA synthetase and diacylglycerol acyltransferase contribute to enrichment of flax seed oil with α-linolenic acid

2018 ◽  
Vol 475 (8) ◽  
pp. 1473-1489 ◽  
Author(s):  
Yang Xu ◽  
Roman Holic ◽  
Darren Li ◽  
Xue Pan ◽  
Elzbieta Mietkiewska ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Linolenic Acid ◽  
Seed Oil ◽  
Diacylglycerol Acyltransferase ◽  
Acyl Donor ◽  
Flax Seed ◽  
Chain Acyl ◽  
Long Chain

Seed oil from flax (Linum usitatissimum) is enriched in α-linolenic acid (ALA; 18:3Δ9cis,12cis,15cis), but the biochemical processes underlying the enrichment of flax seed oil with this polyunsaturated fatty acid are not fully elucidated. Here, a potential process involving the catalytic actions of long-chain acyl-CoA synthetase (LACS) and diacylglycerol acyltransferase (DGAT) is proposed for ALA enrichment in triacylglycerol (TAG). LACS catalyzes the ATP-dependent activation of free fatty acid to form acyl-CoA, which in turn may serve as an acyl-donor in the DGAT-catalyzed reaction leading to TAG. To test this hypothesis, flax LACS and DGAT cDNAs were functionally expressed in Saccharomyces cerevisiae strains to probe their possible involvement in the enrichment of TAG with ALA. Among the identified flax LACSs, LuLACS8A exhibited significantly enhanced specificity for ALA over oleic acid (18:1Δ9cis) or linoleic acid (18:2Δ9cis,12cis). Enhanced α-linolenoyl-CoA specificity was also observed in the enzymatic assay of flax DGAT2 (LuDGAT2-3), which displayed ∼20 times increased preference toward α-linolenoyl-CoA over oleoyl-CoA. Moreover, when LuLACS8A and LuDGAT2-3 were co-expressed in yeast, both in vitro and in vivo experiments indicated that the ALA-containing TAG enrichment process was operative between LuLACS8A- and LuDGAT2-3-catalyzed reactions. Overall, the results support the hypothesis that the cooperation between the reactions catalyzed by LACS8 and DGAT2 may represent a route to enrich ALA production in the flax seed oil.

Inhibitory Effect of Long Chain Fatty Acyl CoAs on RNA Polymerase from Escherichia coli1

1983 ◽  
Vol 94 (2) ◽  
pp. 415-420
Author(s):  
Masayuki YOKOKAWA ◽  
Akiko FUJIWARA ◽  
Hiraku SHIMADA ◽  
Ikuo YASUMASU
Keyword(s):  
Rna Polymerase ◽  
Inhibitory Effect ◽  
Fatty Acyl ◽  
Long Chain

scholarly journals Elevation of 20-carbon long chain bases due to a mutation in serine palmitoyltransferase small subunit b results in neurodegeneration

2015 ◽  
Vol 112 (42) ◽  
pp. 12962-12967 ◽  
Author(s):  
Lihong Zhao ◽  
Stefka Spassieva ◽  
Kenneth Gable ◽  
Sita D. Gupta ◽  
Lan-Ying Shi ◽  
...  
Keyword(s):  
Chain Length ◽  
Small Subunit ◽  
Fatty Acyl ◽  
Substrate Affinity ◽  
Serine Palmitoyltransferase ◽  
Membrane Structures ◽  
Long Chain Base ◽  
Chain Lengths ◽  
Long Chain

Sphingolipids typically have an 18-carbon (C18) sphingoid long chain base (LCB) backbone. Although sphingolipids with LCBs of other chain lengths have been identified, the functional significance of these low-abundance sphingolipids is unknown. The LCB chain length is determined by serine palmitoyltransferase (SPT) isoenzymes, which are trimeric proteins composed of two large subunits (SPTLC1 and SPTLC2 or SPTLC3) and a small subunit (SPTssa or SPTssb). Here we report the identification of an Sptssb mutation, Stellar (Stl), which increased the SPT affinity toward the C18 fatty acyl-CoA substrate by twofold and significantly elevated 20-carbon (C20) LCB production in the mutant mouse brain and eye, resulting in surprising neurodegenerative effects including aberrant membrane structures, accumulation of ubiquitinated proteins on membranes, and axon degeneration. Our work demonstrates that SPT small subunits play a major role in controlling SPT activity and substrate affinity, and in specifying sphingolipid LCB chain length in vivo. Moreover, our studies also suggest that excessive C20 LCBs or C20 LCB-containing sphingolipids impair protein homeostasis and neural functions.

Carnitine palmitoyltransferases in pea leaf chloroplasts: partial purification, location, and properties

2000 ◽  
Vol 78 (3) ◽  
pp. 328-335 ◽  
Author(s):  
Christine Masterson ◽  
Clifford Wood
Keyword(s):  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Carnitine Palmitoyltransferase ◽  
Chloroplast Envelope ◽  
Partial Purification ◽  
Western Blots ◽  
Chain Acyl ◽  
Long Chain ◽  
Inner Envelope

Carnitine palmitoyltransferase (EC 2.3.1.21), an enzyme that catalyses the reversible transfer of activated long-chain acyl groups between CoASH and L-carnitine, has been confirmed in pea leaf chloroplasts. This enzyme is bound to the chloroplast inner envelope membrane and has two isoforms, one bound to the outside (cytosol side) of the inner envelope and one bound to the inside (stromal side) of the inner envelope. Malonyl CoA inhibited the activity of the outer carnitine palmitoyltransferase, while stimulating the activity of the inner isoform and may be a regulator of these enzymes in vivo. Carnitine palmitoyltransferase was solubilized from the chloroplast envelope by detergent treatment and the two isoforms separated by Q-Sepharose anion exchange chromatography. Both proteins were immunochemically observed by probing Western blots of sodium dodecyl sulfate - polyacrylamide gel electrophoresis gels using an anti-beef heart mitochondrial carnitine palmitoyltransferase polyclonal antibody. The monomeric molecular mass of the protein recognized by this antibody was approximately 20 kDa. This 20-kDa protein also bound3H-carnitine. Both isoforms had broad acyl CoA substrate specificities, but showed increased activity with desaturated long-chain acyl CoAs, exhibiting a preference for linolenoyl CoA. A role for carnitine palmitoyltransferase in the shuttling of fatty acids across the chloroplast envelope is suggested.Key words: Pisum sativum, chloroplasts, carnitine palmitoyltransferase, fatty acid metabolism, eukaryotic pathway, membrane transport.

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