共查询到20条相似文献,搜索用时 535 毫秒
1.
Jane L. Wang Scott J. Bowen Barbara A. Schweitzer Heather M. Madsen Joseph McDonald Matthew J. Pelc Ruth E. Tenbrink David Beidler Atli Thorarensen 《Bioorganic & medicinal chemistry letters》2009,19(20):5970-5974
Fatty acid amide hydrolase (FAAH) has attracted significant attention due to its promise as an analgesic target. This has resulted in the discovery of numerous chemical classes as inhibitors of this potential therapeutic target. In this paper we disclose a new series of novel FAAH irreversible azetidine urea inhibitors. In general these compounds illustrate potent activity against the rat FAAH enzyme. Our SAR studies allowed us to optimize this series resulting in the identification of compounds 13 which were potent inhibitors of both human and rat enzyme. This series of compounds illustrated good hydrolase selectivity along with good PK properties. 相似文献
2.
Chemical-induced apoptotic cell death in tomato cells: involvement of caspase-like proteases 总被引:16,自引:0,他引:16
A new system to study programmed cell death in plants is described. Tomato (Lycopersicon esculentum Mill.) suspension cells were induced to undergo programmed cell death by treatment with known inducers of apoptosis in mammalian
cells. This chemical-induced cell death was accompanied by the characteristic features of apoptosis in animal cells, such
as typical changes in nuclear morphology, the fragmentation of the nucleus and DNA fragmentation. In search of processes involved
in plant apoptotic cell death, specific enzyme inhibitors were tested for cell-death-inhibiting activity. Our results showed
that proteolysis plays a crucial role in apoptosis in plants. Furthermore, caspase-specific peptide inhibitors were found
to be potent inhibitors of the chemical-induced cell death in tomato cells, indicating that, as in animal systems, caspase-like
proteases are involved in the apoptotic cell death pathway in plants.
Received: 5 August 1999 / Accepted: 14 March 2000 相似文献
3.
《Bioorganic & medicinal chemistry》2019,27(23):115096
FAAH inhibitors offer safety advantages by augmenting the anandamide levels “on demand” to promote neuroprotective mechanisms without the adverse psychotropic effects usually seen with direct and chronic activation of the CB1 receptor. FAAH is an enzyme implicated in the hydrolysis of the endocannabinoid N-arachidonoylethanolamine (AEA), which is a partial agonist of the CB1 receptor. Herein, we report the discovery of a new series of highly potent and selective carbamate FAAH inhibitors and their evaluation for neuroprotection. The new inhibitors showed potent nanomolar inhibitory activity against human recombinant and purified rat FAAH, were selective (>1000-fold) against serine hydrolases MGL and ABHD6 and lacked any affinity for the cannabinoid receptors CB1 and CB2. Evaluation of FAAH inhibitors 9 and 31 using the in vitro competitive activity-based protein profiling (ABPP) assay confirmed that both inhibitors were highly selective for FAAH in the brain, since none of the other FP-reactive serine hydrolases in this tissue were inhibited by these agents. Our design strategy followed a traditional SAR approach and was supported by molecular modeling studies based on known FAAH cocrystal structures. To rationally design new molecules that are irreversibly bound to FAAH, we have constructed “precovalent” FAAH-ligand complexes to identify good binding geometries of the ligands within the binding pocket of FAAH and then calculated covalent docking poses to select compounds for synthesis. FAAH inhibitors 9 and 31 were evaluated for neuroprotection in rat hippocampal slice cultures. In the brain tissue, both inhibitors displayed protection against synaptic deterioration produced by kainic acid-induced excitotoxicity. Thus, the resultant compounds produced through rational design are providing early leads for developing therapeutics against seizure-related damage associated with a variety of disorders. 相似文献
4.
Summary. Glucocorticoid hormones enhance the reabsorptive capacity of filtered amino acids in rat kidney, as it was shown in previous
in vivo clearance experiments. In the present study, the site of glucocorticoid action on neutral amino acid transport in superficial
nephrons of rat kidney was investigated using in vivo micropuncture technique. Adult female Wistar rats were treated with dexamethasone (DEX), and fractional excretion of L-glutamine
(L-Gln) and L-leucine (L-Leu) were determined and related to inulin after microinfusion into different nephron segments. DEX
reduced fractional excretion of both neutral amino acids as a sign of enhanced reabsorptive capacity. The site of main DEX
action on L-Leu reabsorption has been localized in the proximal straight tubule. However, in the case of L-Gln, the inhibition
of γ-glutamyltranspeptidase (γ-GT) by administration of acivicin indicated the importance of this brush border enzyme in reduced L-Gln excretion. DEX enhanced
γ-GT activity by tubular acidification. It can be presumed a DEX-inducible transport system for neutral amino acids mainly
localized in proximal straight tubules of rat kidney.
Received July 8, 1999 相似文献
5.
Transgenic Nicotiana tabacum and Arabidopsis thaliana plants overexpressing allene oxide synthase 总被引:3,自引:0,他引:3
Allene oxide synthase (AOS), encoded by a single gene in Arabidopsis thaliana (L.) Heynh., catalyzes the first step specific to the octadecanoid pathway. Enzyme activity is very low in control plants,
but is upregulated by wounding, octadecanoids, ethylene, salicylate and coronatine (D. Laudert and E.W. Weiler, 1998, Plant
J 15: 675–684). In order to study the consequences of constitutive expression of AOS on the level of jasmonates, a complete
cDNA encoding the enzyme from A. thaliana was constitutively expressed in both A. thaliana and tobacco (Nicotiana tabacum L.). Overexpression of AOS did not alter the basal level of jasmonic acid; thus, output of the jasmonate pathway in the unchallenged
plant appears to be strictly limited by substrate availability. In wounded plants overexpressing AOS, peak jasmonate levels
were 2- to 3-fold higher compared to untransformed plants. More importantly, the transgenic plants reached the maximum jasmonate
levels significantly earlier than wounded untransformed control plants. These findings suggest that overexpression of AOS
might be a way of controlling defense dynamics in higher plants.
Received: 10 February 2000 / Accepted: 11 March 2000 相似文献
6.
Summary. Trypanosomatids depend on spermidine for growth and survival. Consequently, enzymes involved in spermidine synthesis and utilization,
i.e. arginase, ornithine decarboxylase (ODC), S-adenosylmethionine decarboxylase (AdoMetDC), spermidine synthase, trypanothione synthetase (TryS), and trypanothione reductase
(TryR), are promising targets for drug development. The ODC inhibitor α-difluoromethylornithine (DFMO) is about to become
a first-line drug against human late-stage gambiense sleeping sickness. Another ODC inhibitor, 3-aminooxy-1-aminopropane (APA),
is considerably more effective than DFMO against Leishmania promastigotes and amastigotes multiplying in macrophages. AdoMetDC inhibitors can cure animals infected with isolates from
patients with rhodesiense sleeping sickness and leishmaniasis, but have not been tested on humans. The antiparasitic effects
of inhibitors of polyamine and trypanothione formation, reviewed here, emphasize the relevance of these enzymes as drug targets.
By taking advantage of the differences in enzyme structure between parasite and host, it should be possible to design new
drugs that can selectively kill the parasites. 相似文献
7.
Geranylhydroquinone 3′′-hydroxylase, a cytochrome P-450 monooxygenase from Lithospermum erythrorhizon cell suspension cultures 总被引:2,自引:0,他引:2
Geranylhydroquinone 3′′-hydroxylase, which is likely to be involved in shikonin and dihydroechinofuran biosynthesis, was
identified in cell suspension cultures of Lithospermum erythrorhizon Sieb. et Zucc. (Boraginaceae). The enzyme hydroxylates the isoprenoid side chain of geranylhydroquinone (GHQ), a known precursor
of shikonin. Proton/proton correlation spectroscopic and proton/proton long-range correlation spectroscopic studies confirmed
that hydroxylation takes place specifically at position 3′′, i.e. at the methyl group involved in the cyclization reaction.
The enzyme is membrane-bound and was found in the microsomal fraction. It requires NADPH and molecular oxygen as cofactors,
and is inhibited by cytochrome P-450 inhibitors such as cytochrome c and CO. The inhibitory effect of CO is reversed by illumination.
These data suggest that the enzyme is a cytochrome P-450-dependent monooxygenase. The optimum pH of GHQ 3′′-hydroxylase is
7.4, and the apparent K
m value for GHQ is 1.5 μM. The reaction velocity obtained with 3-geranyl-4-hydroxybenzoic acid was more than 100 times lower
than that obtained with geranylhydroquinone.
Received: 20 March 1999 / Accepted: 20 July 1999 相似文献
8.
Summary. Phosphate transport in bacteria occurs via a phosphate specific transporter system (PSTS) that belongs to the ABC family of
transporters, a multisubunit system, containing an alkaline phosphatase. DING proteins were characterized due to the N-terminal
amino acid sequence DINGG GATL, which is highly conserved in animal and plant isolates, but more variable in microbes. Most
prokaryotic homologues of the DING proteins often have some structural homology to phosphatases or periplasmic phosphate-binding
proteins. In E. coli, the product of the inducible gene DinG, possesses ATP hydrolyzing helicase enzymic activity. An alkaline phosphorolytic enzyme of the PSTS system was purified
to homogeneity from the thermophilic bacterium Thermus thermophilus. N-terminal sequence analysis of this protein revealed the same high degree of similarity to DING proteins especially to
the human synovial stimulatory protein P205, the steroidogenesis-inducing protein and to the phosphate ABC transporter, periplasmic
phosphate-binding protein, putative (P. fluorescens Pf-5). The enzyme had a molecular mass of 40 kDa on SDS/PAGE, exhibiting optimal phosphatase activity at pH 12.3 and 70 °C.
The enzyme possessed characteristics of a DING protein, such as ATPase, ds endonuclease and 3′ phosphodiesterase (3′-exonuclease)
activities and binding to linear dsDNA, displaying helicase activity on supercoiled DNA. Purification and biochemical characterization
of a T. thermophilus DING protein was achieved. The biochemical properties, N-terminal sequence similarities of this protein implied that the
enzyme belongs to the PSTS family and might be involved in the DNA repair mechanism of this microorganism.
Authors’ address: Assist. Prof. A. A. Pantazaki, Laboratory of Biochemistry, Department of Chemistry, Aristotle University
of Thessaloniki, Thessaloniki 54124, Greece 相似文献
9.
Cloning and expression of UDP-glucose: flavonoid 7-O-glucosyltransferase from hairy root cultures of Scutellaria baicalensis 总被引:1,自引:0,他引:1
A cDNA encoding UDP-glucose: baicalein 7-O-glucosyltransferase (UBGT) was isolated from a cDNA library from hairy root cultures of Scutellaria baicalensis Georgi probed with a partial-length cDNA clone of a UDP-glucose: flavonoid 3-O-glucosyltransferase (UFGT) from grape (Vitis vinifera L.). The heterologous probe contained a glucosyltransferase consensus amino acid sequence which was also present in the Scutellaria cDNA clones. The complete nucleotide sequence of the 1688-bp cDNA insert was determined and the deduced amino acid sequences
are presented. The nucleotide sequence analysis of UBGT revealed an open reading frame encoding a polypeptide of 476 amino
acids with a calculated molecular mass of 53 094 Da. The reaction product for baicalein and UDP-glucose catalyzed by recombinant
UBGT in Escherichia coli was identified as authentic baicalein 7-O-glucoside using high-performance liquid chromatography and proton nuclear magnetic resonance spectroscopy. The enzyme activities
of recombinant UBGT expressed in E. coli were also detected towards flavonoids such as baicalein, wogonin, apigenin, scutellarein, 7,4′-dihydroxyflavone and kaempferol,
and phenolic compounds. The accumulation of UBGT mRNA in hairy roots was in response to wounding or salicylic acid treatments.
Received: 8 September 1999 / Accepted: 4 October 1999 相似文献
10.
Summary. The polyamines are growth factors in both normal and cancer cells. As the intracellular polyamine content correlates positively
with the growth potential of that cell, the idea that depletion of polyamine content will result in inhibition of cell growth
and, particularly tumour cell growth, has been developed over the last 15 years. The polyamine pathway is therefore a target
for development of rationally designed, antiproliferative agents. Following the lessons from the single enzyme inhibitors
(α-difluoromethylornithine DFMO), three generations of polyamine analogues have been synthesised and tested in vitro and in vivo. The analogues are multi-site inhibitors affecting multiple reactions in the pathway and thus prevent the up-regulation of
compensatory reactions that have been the downfall of DFMO in anticancer chemotherapy. Although the initial concept was that
the analogues may provide novel anticancer drugs, it now seems likely that the analogues will have wider applications in diseases
involving hyperplasia. 相似文献
11.
Microinjection of heme oxygenase genes rescues phytochrome-chromophore-deficient mutants of the moss Ceratodon purpureus 总被引:1,自引:0,他引:1
In protonemal tip cells of the moss Ceratodon purpureus (Hedw.) Brid., phototropism and chlorophyll accumulation are regulated by the photoreceptor phytochrome. The mutant ptr116 lacks both responses as a result of a defect in the biosynthesis of phytochromobilin, the chromophore of phytochrome, at
the point of biliverdin formation. The rescue of the phototropic response and of chlorophyll synthesis were tested by injecting
different substances into tip cells of ptr116. Microinjection was first optimised with the use of fluorescent dyes and an expression plasmid containing a green fluorescent
protein (GFP) gene. Injected phycocyanobilin, which substitutes for phytochromobilin, rescued both the phototropic response
and light-induced chlorophyll accumulation in ptr116. The same results were obtained when expression plasmids with heme oxygenase genes of rat (HO-1) and Arabidopsis thaliana (L.) Heynh. (HY1) were injected. Heme oxygenase catalyses the conversion of heme into biliverdin. Whereas HY1 has a plastid target sequence
and is presumably transferred to plastids, HO-1 is proposed to be cytosolic. The data show that ptr116 lacks heme oxygenase enzyme activity and indicate that heme oxygenases of various origin are active in Ceratodon bilin synthesis. In addition, it can be inferred from the data that the intracellular localisation of the expressed heme
oxygenase is not important since the plastid enzyme can be replaced by a cytosolic one.
Received: 8 March 1999 / Accepted: 30 July 1999 相似文献
12.
Summary. Protein L4 from the thermophilic bacterium Thermus thermophilus (TthL4) was heterologously overproduced in Escherichia coli cells and purified under native conditions by using ion exchange chromatography. Although it’s known strong binding to RNA
(23S rRNA as well as mRNA) the yield of the purified protein was 6 mg per 10 g of cells and it is similar to that referred
for Thermotoga maritima L4 ribosomal protein.
In addition, E. coli cells harboring the wild type Thermus thermophilus L4 (wtTthL4) ribosomal protein as well as its mutant having changed the highly conserved glutamic acid 56 by alanine (TthL4-Ala
56) were incorporated into E. coli ribosomes after transformation of the host cells with the recombined vector. The cells having incorporated the mutant TthL4-Ala56
are more sensitive against erythromycin related to that containing the wtTthL4 protein.
The resistance to the drug indicates that the mutated amino acid Glu56 is probably critical for the local ribosomal conformation
and that its mutation induces conformational disturbances that are “transferred” to the entrance of the major exit tunnel,
the place where the drug does bind. 相似文献
13.
Calderón-Cortés E Clemente-Guerrero M Sierra-Campos E Cortés-Rojo C Gaona-Zamudio FJ Villalobos-Molina R Saavedra-Molina A 《Amino acids》2006,31(1):73-80
Summary. Starting from a collection of 1386 druggable compounds obtained from the 3D pharmacophore search, we performed a similarity
search to narrow down the scope of docking studies. The template molecule is KZ7088 (Chou et al., 2003, Biochem Biophys Res Commun 308: 148–151). The MDL MACCS keys were used to fingerprint the molecules. The Tanimoto coefficient is taken as the metric
to compare fingerprints. If the similarity threshold was 0.8, a set of 50 unique hits and 103 conformers were retrieved as
a result of similarity search. The AutoDock 3.011 was used to carry out molecular docking of 50 ligands to their macromolecular
protein receptors. Three compounds, i.e., C28H34O4N7Cl, C21H36O5N6, and C21H36O5N6, were found that may be promising candidates for further investigation. The main feature shared by these three potential
inhibitors as well as the information of the involved side chains of SARS Cov Mpro may provide useful insights for the development
of potent inhibitors against SARS enzyme. 相似文献
14.
Summary. Owing to their chemical reactivity, radicals have cytocidal properties. Destruction of cells by irradiation-induced radical
formation is one of the most frequent interventions in cancer therapy. An alternative to irradiation-induced radical formation
is in principle drug-induced formation of radicals, and the formation of toxic metabolites by enzyme catalysed reactions.
Although these developments are currently still in their infancy, they nevertheless deserve consideration. There are now numerous
examples known of conventional anti-cancer drugs that may at least in part exert cytotoxicity by induction of radical formation.
Some drugs, such as arsenic trioxide and 2-methoxy-estradiol, were shown to induce programmed cell death due to radical formation.
Enzyme-catalysed radical formation has the advantage that cytotoxic products are produced continuously over an extended period
of time in the vicinity of tumour cells. Up to now the enzymatic formation of toxic metabolites has nearly exclusively been
investigated using bovine serum amine oxidase (BSAO), and spermine as substrate. The metabolites of this reaction, hydrogen
peroxide and aldehydes are cytotoxic. The combination of BSAO and spermine is not only able to prevent tumour cell growth,
but prevents also tumour growth, particularly well if the enzyme has been conjugated with a biocompatible gel. Since the tumour
cells release substrates of BSAO, the administration of spermine is not required. Combination with cytotoxic drugs, and elevation
of temperature improves the cytocidal effect of spermine metabolites. The fact that multidrug resistant cells are more sensitive
to spermine metabolites than their wild type counterparts makes this new approach especially attractive, since the development
of multidrug resistance is one of the major problems of conventional cancer therapy. 相似文献
15.
Lucyna Kubiak-Martens 《Vegetation History and Archaeobotany》2002,11(1-2):23-32
Roots and tubers, together with other plant storage organs such as rhizomes, bulbs, corms, etc. are known to be a source
of human food. Until very recently, however, remains of root foods were rarely identified from archaeological contexts in
temperate Europe. New evidence for the use of root foods has been recently recovered from the early Erteb?lle settlement at
Halsskov in Denmark. Remains included charred bulbs of Allium cf. ursinum and tubers of Conopodium majus. They were accompanied by charred remains of parenchymatous tissues derived from underground parts of other plants. All parenchymatous
remains were recovered from features that could be interpreted as pit-cooking depressions. A minimum of two periods of root
food gathering can be assumed, spring to early summer and autumn. The presence of charred seeds of Nuphar pumilum suggests that either the seeds or rhizomes (or both) were use as food.
Received September 4, 2001 / Accepted February 27, 2002 相似文献
16.
Summary.
Background. Perinatal asphyxia is a frequent cause of neurological handicap with no known therapy. However, hypothermic therapy has
recently attracted attention owing to its neuroprotective property in brain of immature organisms.
Objectives. Hypothermia appears to be promising in reversing the immediate effect of perinatal asphyxia, but data on long-term neuroprotection
is still lacking. We therefore intended to test the long-term effect of moderate and profound hypothermia on brain morphology
and functions using a well established rat model of perinatal asphyxia.
Methods. Rat pups delivered by caesarean section were placed into a water bath, still in patent membranes, at 37 °C and variable
hypothermic conditions to induce asphyxia and thereafter given to surrogate mothers. Examinations were performed at the age
of three months, consisting of a battery of motor, behavioural, cognition and reflex tests including rota-rod, Morris water
maze, multiple T-maze, elevated plus maze and open field studies. Morphological alterations were evaluated by Nissl staining
of brain areas known to be hypoxia sensitive. Neurotransmission system markers, including tyrosine hydroxylase, vesicular
monoamine transporter, vesicular acetylcholine transporter and excitatory amino acid carrier1 were analyzed by immunohistochemistry.
Results. Survival increased with hypothermia. The Nissl stain revealed neuronal loss in hippocampus and hypothalamus of normothermic
asphyxiated group (20/37) compared to controls (0/37), but no neuroprotective patterns emerged from hypothermia. An overall
inconsistent protection of the neural systems was noted by variable periods of hypothermia. Motor function was significantly
impaired in 20/37 as compared to 0/37. In the Morris water maze and multiple T-maze, results were comparable between the groups.
In the elevated plus maze, time spent in the closed arm was reduced and in the open field, vertical behaviour was altered
in the 20/37 group with horizontal motor behaviour being unaffected. Hypothermia reversed all abnormalities seen in 20/37,
with short-term moderate and profound hypothermia being superior to long-term hypothermia.
Conclusion. Hypothermia not only significantly increased survival, but also resulted in unimpaired motor as well as improved cognitive
functions. Those findings are in contrast to altered brain morphology. As neuronal loss was present in various brain regions,
we conclude that deficits may be compensated in the maturing animal. Intrahypoxic hypothermia was able to protect the rat
from the devastating effect of perinatal asphyxia not in morphological, but in functional terms.
The first and third authors have contributed equally to this work. 相似文献
17.
Jessica Karlsson Carmine M. Morgillo Alessandro Deplano Giovanni Smaldone Emilia Pedone F. Javier Luque Mona Svensson Ettore Novellino Cenzo Congiu Valentina Onnis Bruno Catalanotti Christopher J. Fowler 《PloS one》2015,10(11)
Background
Combined fatty acid amide hydrolase (FAAH) and cyclooxygenase (COX) inhibition is a promising approach for pain-relief. The Flu-AM1 and Ibu-AM5 derivatives of flurbiprofen and ibuprofen retain similar COX-inhibitory properties and are more potent inhibitors of FAAH than the parent compounds. However, little is known as to the nature of their interaction with FAAH, or to the importance of their chirality. This has been explored here.Methodology/Principal Findings
FAAH inhibitory activity was measured in rat brain homogenates and in lysates expressing either wild-type or FAAHT488A-mutated enzyme. Molecular modelling was undertaken using both docking and molecular dynamics. The (R)- and (S)-enantiomers of Flu-AM1 inhibited rat FAAH with similar potencies (IC50 values of 0.74 and 0.99 μM, respectively), whereas the (S)-enantiomer of Ibu-AM5 (IC50 0.59 μM) was more potent than the (R)-enantiomer (IC50 5.7 μM). Multiple inhibition experiments indicated that both (R)-Flu-AM1 and (S)-Ibu-AM5 inhibited FAAH in a manner mutually exclusive to carprofen. Computational studies indicated that the binding site for the Flu-AM1 and Ibu-AM5 enantiomers was located between the acyl chain binding channel and the membrane access channel, in a site overlapping the carprofen binding site, and showed a binding mode in line with that proposed for carprofen and other non-covalent ligands. The potency of (R)-Flu-AM1 was lower towards lysates expressing FAAH mutated at the proposed carprofen binding area than in lysates expressing wild-type FAAH.Conclusions/Significance
The study provides kinetic and structural evidence that the enantiomers of Flu-AM1 and Ibu-AM5 bind in the substrate channel of FAAH. This information will be useful in aiding the design of novel dual-action FAAH: COX inhibitors. 相似文献18.
Oleg Sadovski Justin W. Hicks Jun Parkes Roger Raymond José Nobrega Sylvain Houle Mariateresa Cipriano Christopher J. Fowler Neil Vasdev Alan A. Wilson 《Bioorganic & medicinal chemistry》2013,21(14):4351-4357
Fatty acid amide hydrolase (FAAH), the enzyme responsible for terminating signaling by the endocannabinoid anandamide, plays an important role in the endocannabinoid system, and FAAH inhibitors are attractive drugs for pain, addiction, and neurological disorders. The synthesis, radiosynthesis, and evaluation, in vitro and ex vivo in rat, of an 18F-radiotracer designed to image FAAH using positron emission tomography (PET) is described.Fluorine-18 labelled 3-(4,5-dihydrooxazol-2-yl)phenyl (5-fluoropentyl)carbamate, [18F]5, was synthesized at high specific activity in a one-pot three step reaction using a commercial module with a radiochemical yield of 17–22% (from [18F]fluoride). In vitro assay using rat brain homogenates showed that 5 inhibited FAAH in a time-dependent manner, with an IC50 value of 0.82 nM after a preincubation of 60 min. Ex vivo biodistribution studies and ex vivo autoradiography in rat brain demonstrated that [18F]5 had high brain penetration with standard uptake values of up to 4.6 and had a regional distribution which correlated with reported regional FAAH enzyme activity. Specificity of binding to FAAH with [18F]5 was high (>90%) as demonstrated by pharmacological challenges with potent and selective FAAH inhibitors and was irreversible as demonstrated by radioactivity measurements on homogenized brain tissue extracts.We infer from these results that [18F]5 is a highly promising candidate radiotracer with which to image FAAH in human subjects using PET and clinical studies are proceeding. 相似文献
19.
20.
Membrane phospholipids represent a potential influence on the enzymatic properties of the Na,K-ATPase. Little is known concerning
the effects of the fatty acid environment surrounding the enzyme on the kinetic properties of the Na,K-ATPase. We used the
most obvious difference among the α isoforms of rat, their affinities for digitalis glycosides, to examine the relationship
between the lipid environment and the Na,K-ATPase. Specific membrane environments that differ in their fatty acid composition
were produced by drug-induced diabetes, as well as variations in diet. The α1 isoforms in various tissues were then characterized
by their resistance to ouabain in Na,K-ATPase-enriched membrane microsomal fractions. The Na,K-ATPase activity in nerves and
hearts were altered by diabetes and partially restored in nerves after a fish oil diet. Evaluation of enzyme kinetics (dose-response
curves for ouabain) in membrane preparations allowed us to correlate the ouabain affinity of α1 isoform with fatty acid composition.
The affinity of the α1 isoform for ouabain was significantly increased with accretions in the total amount of fatty acids
of the n-6 series (P < 0.0001). Our observations provide a partial explanation for the observed difference in isoform properties among tissues.
Moreover, these results underline the interaction between membrane fatty acids and the glycoside binding site of the Na,K-ATPase
α1 subunit.
Received: 15 June 1998/Revised: 18 November 1998 相似文献