共查询到20条相似文献,搜索用时 15 毫秒
1.
Lenz H Schmidt M Welge V Kueper T Schlattner U Wallimann T Elsässer HP Wittern KP Wenck H Staeb F Blatt T 《Molecular and cellular biochemistry》2007,306(1-2):153-162
The creatine kinase (CK) system is essential for cellular energetics in tissues or cells with high and fluctuating energy
requirements. Creatine itself is known to protect cells from stress-induced injury. By using an siRNA approach to silence
the CK isoenzymes in human keratinocyte HaCaT cells, expressing low levels of cytoplasmic CK and high levels of mitochondrial
CK, as well as HeLa cancer cells, expressing high levels of cytoplasmic CK and low levels of mitochondrial CK, we successfully
lowered the respective CK expression levels and studied the effects of either abolishing cytosolic brain-type BB-CK or ubiquitous
mitochondrial uMi-CK in these cells. In both cell lines, targeting the dominant CK isoform by the respective siRNAs had the
strongest effect on overall CK activity. However, irrespective of the expression level in both cell lines, inhibition of the
mitochondrial CK isoform generally caused the strongest decline in cell viability and cell proliferation. These findings are
congruent with electron microscopic data showing substantial alteration of mitochondrial morphology as well as mitochondrial
membrane topology after targeting uMi-CK in both cell lines. Only for the rate of apoptosis, it was the least expressed CK
present in each of the cell lines whose inhibition led to the highest proportion of apoptotic cells, i.e., downregulation
of uMi-CK in case of HeLaS3 and BB-CK in case of HaCaT cells. We conclude from these data that a major phenotype is linked
to reduction of mitochondrial CK alone or in combination with cytosolic CK, and that this effect is independent of the relative
expression levels of Mi-CK in the cell type considered. The mitochondrial CK isoform appears to play the most crucial role
in maintaining cell viability by stabilizing contact sites between inner and outer mitochondrial membranes and maintaining
local metabolite channeling, thus avoiding transition pore opening which eventually results in activation of caspase cell-death
pathways. 相似文献
2.
Some evidences for creatine kinase activity in normal human erythrocyte membrane were presented. The creatine kinase was indicated to be a constituent of the integral proteins of erythrocyte membrane or to be tightly bound to the membrane, and was contrasted to the results obtained with adenylate kinase. Isoenzyme distribution of the erythrocyte creatine kinase by electrophoresis was identical to MM-creatine kinase from rabbit muscle. 相似文献
3.
Roland Schricker Viktor Magdolen Wolfhard Bandlow 《Molecular & general genetics : MGG》1992,233(3):363-371
Summary Making use of the polymerase chain reaction primed by oligonucleotides corresponding to regions conserved between members of the nucleoside monophosphate kinase family, we have isolated the yeast gene PAK3. Pak3p belongs to the subgroup of long-form adenylate kinase isozymes (deduced molecular mass 25.3 kDa) and exhibits highest sequence similarity to bovine AK3 rather than to the yeast isozyme, Aky2p. The gene is shown to be non-essential because haploid disruption mutants are viable, both in the presence and absence of a functional AKY2 allele. It maps on chromosome V upstream of RAD3. Its expression level is low when cells are grown on glucose or other fermentable carbon sources and about threefold higher on glycerol, but can be significantly induced by ethanol. A PAK3/mouse dihydrofolate reductase fusion construct expressed in yeast is targeted to mitochondria. Transformation with PAK3 on a multicopy plasmid complements neither adenylate kinase deficiency in an aky2-disrupted yeast strain nor in Escherichia coli cells conditionally defective in adenylate kinase.Abbreviations Ap5A
P1,P5-di(adenosine-5)pentaphosphate
- adenylate kinase
ATP: AMP phosphotransferase (EC 2.7.4.3)
- Pak3p (Aky2p)
protein product of the PAK3 (AKY2) gene
- DHFR
mouse dihydrofolate reductase 相似文献
4.
The main focus of this investigation is steady state kinetics of regulation of mitochondrial respiration in permeabilized cardiomyocytes in situ. Complete kinetic analysis of the regulation of respiration by mitochondrial creatine kinase was performed in the presence of pyruvate kinase and phosphoenolpyruvate to simulate interaction of mitochondria with glycolytic enzymes. Such a system analysis revealed striking differences in kinetic behaviour of the MtCK-activated mitochondrial respiration in situ and in vitro. Apparent dissociation constants of MgATP from its binary and ternary complexes with MtCK, Kia and Ka (1.94 ± 0.86 mM and 2.04 ± 0.14 mM, correspondingly) were increased by several orders of magnitude in situ in comparison with same constants in vitro (0.44 ± 0.08 mM and 0.016 ± 0.01 mM, respectively). Apparent dissociation constants of creatine, Kib and Kb (2.12 ± 0.21 mM 2.17 ± 0.40 Mm, correspondingly) were significantly decreased in situ in comparison with in vitro mitochondria (28 ± 7 mM and 5 ± 1.2 mM, respectively). Dissociation constant for phosphocreatine was not changed. These data may indicate selective restriction of metabolites' diffusion at the level of mitochondrial outer membrane. It is concluded that mechanisms of the regulation of respiration and energy fluxes in vivo are system level properties which depend on intracellular interactions of mitochondria with cytoskeleton, intracellular MgATPases and cytoplasmic glycolytic system. 相似文献
5.
Luc Passera Laurent Keller 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1990,160(2):207-211
Summary In ants, energy for flying is derived from carbohydrates (glycogen and free sugars). The amount of these substrates was compared in sexuals participating or not participating in mating flights. Results show that in participating females (Lasius niger, L. flavus, Myrmica scabrinodis, Formica rufa, F. polyctena, F. lugubris), the amount of carbohydrates, especially glycogen, was higher than in non-participating females (Cataglyphis cursor, Iridomyrmex humilis). Similarly, male C. cursor and I. humilis which fly, exhibit a much higher carbohydrate content than do the non-flying females of these species. Furthermore, the quantity of carbohydrates stored was generally higher in males than in females for each species. These results are discussed with regard to the loss of the nuptial flight by some species of ants. 相似文献
6.
Natalia Timohhina Rita Guzun Kersti Tepp Claire Monge Minna Varikmaa Heiki Vija Peeter Sikk Tuuli Kaambre Dan Sackett Valdur Saks 《Journal of bioenergetics and biomembranes》2009,41(3):259-275
The aim of this study was to measure energy fluxes from mitochondria in isolated permeabilized cardiomyocytes. Respiration
of permeabilized cardiomyocytes and mitochondrial membrane potential were measured in presence of MgATP, pyruvate kinase –
phosphoenolpyruvate and creatine. ATP and phosphocreatine concentrations in medium surrounding cardiomyocytes were determined.
While ATP concentration did not change in time, mitochondria effectively produced phosphocreatine (PCr) with PCr/O2 ratio equal to 5.68 ± 0.14. Addition of heterodimeric tubulin to isolated mitochondria was found to increase apparent Km
for exogenous ADP from 11 ± 2 μM to 330 ± 47 μM, but creatine again decreased it to 23 ± 6 μM. These results show directly
that under physiological conditions the major energy carrier from mitochondria into cytoplasm is PCr, produced by mitochondrial
creatine kinase (MtCK), which functional coupling to adenine nucleotide translocase is enhanced by selective limitation of
permeability of mitochondrial outer membrane within supercomplex ATP Synthasome-MtCK-VDAC-tubulin, Mitochondrial Interactosome. 相似文献
7.
Birkedal R Gesser H 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2004,174(3):255-262
In skinned rat cardiac fibres, mitochondrial affinity for endogenous ADP generated by creatine kinase and Ca2+-activated ATPases is higher than for exogenous ADP added to the surrounding medium, suggesting that mitochondria are functionally coupled to creatine kinase and ATPases. Such a coupling may be weaker or absent in ectothermic vertebrate cardiac cells, because they typically have less elaborate intracellular membrane structures, higher glycolytic capacity and lower working temperature. Therefore, we examined skinned cardiac fibres from rainbow trout at 10 °C. The apparent mitochondrial affinity for endogenous ADP was obtained by stimulation with ATP and recording of the release of ADP into the surrounding medium. The apparent affinity for endogenous ADP was much higher than for exogenous ADP suggesting a functional coupling between mitochondria and ATPases. The apparent affinity for exogenous ADP and ATP was increased by creatine or an increase in Ca2+-activity, which should increase intrafibrillar turnover of ATP to ADP. In conclusion, ADP seems to be channelled from creatine kinase and ATPases to mitochondria without being released to the surrounding medium. Thus, despite difference in structure, temperature and metabolic capacity, trout myocardium resembles that of rat with regard to the regulation of mitochondrial respiration.Abbreviations ACR acceptor control ratio - ANT adenine nucleotide translocase - KM ADP apparent mitochondrial affinity for ADP - KM ATP apparent mitochondrial affinity for ATP - LDH lactate dehydrogenase - VADP ADP-stimulated respiration rate - VADP max maximal ADP-stimulated respiration rate - VATP ATP-stimulated respiration rate - VATP max maximal ATP-stimulated respiration rate - V0 basal respiration rate in the absence of ADPCommunicated by G. Heldmaier 相似文献
8.
A two-compartment kinetic model was used to describe reconstituted systems in which mitochondria compete with pyruvate kinase for kinase-generated ADP. The modelling suggests that cytosolic CK deficiency results in a 50% increase in outer mitochondrial membrane permeability. 相似文献
9.
Suzuki T Mizuta C Uda K Ishida K Mizuta K Sona S Compaan DM Ellington WR 《Journal of molecular evolution》2004,59(2):218-226
Creatine kinase (CK) plays a central role in energy homeostasis in cells that display high and variable rates of energy turnover. A number of CK genes exist, each being targeted to particular intracellular compartments. In the vertebrates, two genes code for proteins which form homo- and heterodimers targeted to the cytoplasm, while two additional genes code for primarily octameric proteins targeted to the mitochondrial intermembrane space. Yet another gene is present in certain groups which codes for three fused, complete CK domains and is typically targeted to the flagellar membrane of primitive-type spermatozoa. CK is widely distributed in protochordates and both protostome and deuterostome invertebrate groups. The evolutionary relationships of these CK genes have not been fully elucidated. The present communication reports new cDNA-derived deduced amino acid sequences for four cytoplasmic and three mitochondrial CKs and one flagellar CK from lophotrochozoan, protostome invertebrates as well as a new cytoplasmic CK sequence from a protochordate tunicate. These new sequences, coupled with available sequences in the databases and sequences extracted from genome sequencing projects, provide revealing insights into the evolution and divergence of CK genes. Phylogenetic analyses showed that single cytoplasmic, mitochondrial, and flagellar CK genes were present prior to the divergence of the protostomes and deuterostomes. The flagellar CK gene may have evolved within the cytoplasmic gene clade, although the evidence is somewhat equivocal. The two cytoplasmic genes in the vertebrates, and most likely the two mitochondrial genes, evolved after the divergence of the craniates from the protochordates. Comparison of the structure of the genes for selected cytoplasmic, mitochondrial, and flagellar CKs revealed two identical intron boundaries, further reinforcing the notion of a common evolutionary origin, but also showed patterns of changes in structure consistent with each gene type. These studies show that the cytoplasmic, mitochondrial, and flagellar CK genes are rather ancient and that there has been a systematic pattern of duplication and divergence consistent with changing nature of energy demands and physicochemical environment in the cells where they are expressed.[Reviewing Editor: Martin Kreitman] 相似文献
10.
Inhibition of mitochondrial respiratory chain in brain of rats subjected to an experimental model of depression 总被引:1,自引:0,他引:1
Rezin GT Cardoso MR Gonçalves CL Scaini G Fraga DB Riegel RE Comim CM Quevedo J Streck EL 《Neurochemistry international》2008,53(6-8):395-400
Depressive disorders, including major depression, are serious and disabling. However, the exact pathophysiology of depression is not clearly understood. Life stressors contribute in some fashion to depression and are an extension of what occurs normally. In this context, chronic stress has been used as an animal model of depression. Based on the hypothesis that metabolism impairment might be involved in the pathophysiology of depression, in the present work we evaluated the activities of mitochondrial respiratory chain complexes and creatine kinase in brain of rats subjected to chronic stress. After 40 days of mild stress, a reduction in sweet food ingestion was observed, as well as increased adrenal gland weight, when compared to control group. We also verified that control group gained weight after 40 days, but stressed group did not. Moreover, our findings showed that complex I, III and IV were inhibited in stress group only in cerebral cortex and cerebellum. On the other hand, complex II and creatine kinase were not affected in stressed group. Although it is difficult to extrapolate our findings to the human condition, the inhibition of mitochondrial respiratory chain by chronic stress may be one mechanism in the pathophysiology of depressive disorders. 相似文献
11.
Marie-Lise Lacombe Malgorzata Tokarska-Schlattner Raquel F. Epand Mathieu Boissan Richard M. Epand Uwe Schlattner 《Biochimie》2009
Nucleoside diphosphate kinases (NDPKs/Nm23), responsible for intracellular di- and tri-phosphonucleoside homeostasis, play multi-faceted roles in cellular energetic, signaling, proliferation, differentiation and tumor invasion. The mitochondrial NDPK-D, the NME4 gene product, is a peripheral protein of the inner membrane. Several new aspects of the interaction of NDPK-D with the inner mitochondrial membrane have been recently characterized. Surface plasmon resonance analysis using recombinant NDPK-D and different phospholipid liposomes showed that NDPK-D interacts electrostatically with anionic phospholipids, with highest affinity observed for cardiolipin, a phospholipid located mostly in the mitochondrial inner membrane. Mutation of the central arginine (R90) in a surface exposed cationic RRK motif unique to NDPK-D strongly reduced phospholipid interaction in vitro and in vivo. Stable expression of NDPK-D proteins in HeLa cells naturally almost devoid of this isoform revealed a tight functional coupling of NDPK-D with oxidative phosphorylation that depends on the membrane-bound state of the enzyme. Owing to its symmetrical hexameric structure exposing membrane binding motifs on two opposite sides, NDPK-D could bridge liposomes containing anionic phospholipids and promote lipid transfer between them. In vivo, NDPK-D could induce intermembrane contacts and facilitate lipid movements between mitochondrial membranes. Most of these properties are reminiscent to those of the mitochondrial creatine kinase. We review here the common properties of both kinases and we discuss their potential roles in mitochondrial functions such as energy production, apoptosis and mitochondrial dynamics. 相似文献
12.
Rodrigo Barbosa Gonçalves 《Revista Brasileira de Entomologia》2019,63(1):91-100
The Augochlora clade includes four genera: Augochlora Smith, Augochlorella Sandhouse, Ceratalictus Moure, and Pereirapis Moure. This is one of the richest and most widespread groups of Augochlorini bees. There are about 150 species, which occur from Argentina to Canada. The species of Augochlora clade are considered solitary to facultatively social, except Ceratalictus for which nothing is known. Wood nesting behavior arose once in the clade, in Augochlora sensu strictu. The objective of this study is to describe four new species and to present a revised phylogenetic analysis of the Augochlora clade for the placement of these species. The morphological matrix comprised 77 characters and 42 terminals, and resulted in two most parsimonious trees. The monophyly of the Augochlora clade is corroborated. Ceratalictus and Pereirapis are considered as sister groups and Ceratalictus inflexus sp. nov. came as sister to other species of Ceratalictus. Augochlora and Augochlorella are monophyletic and sister groups. Both extant subgenera of Augochlora were corroborated as monophyletic. Augochlorella comis is considered as sister group to the rest of Augochlorella species. All Augochlorella new species described belong to the Augochlorella ephyra group. Augochlorella kelliae sp. nov. is phylogenetically related to Augochlorella una. Augochlorella procliva sp. nov. and Augochlorella mavricera sp. nov. constitute a clade with Augochlorella acarinata. Including the new species, Augochlorella has 19 species and Ceratalictus 11 species. A revised key for species of Augochlorella and Ceratalictus is also presented in the Supplementary Information. 相似文献
13.
Saffary R Nandakumar R Spencer D Robb FT Davila JM Swartz M Ofman L Thomas RJ DiRuggiero J 《FEMS microbiology letters》2002,215(1):163-168
We have recovered new isolates from hot springs, in Yellowstone National Park and the Kamchatka Peninsula, after gamma-irradiation and exposure to high vacuum (10(-6) Pa) of the water and sediment samples. The resistance to desiccation and ionizing radiation of one of the isolates, Bacillus sp. strain PS3D, was compared to that of the mesophilic bacterium, Deinococcus radiodurans, a species well known for its extraordinary resistance to desiccation and high doses of ionizing radiation. Survival of these two microorganisms was determined in real and simulated space conditions, including exposure to extreme UV radiation (10-100 nm) during a rocket flight. We found that up to 15 days of desiccation alone had little effect on the viability of either bacterium. In contrast, exposure to space vacuum ( approximately 10(-6) Pa) decreased cell survival by two and four orders of magnitude for Bacillus sp. strain PS3D and D. radiodurans, respectively. Simultaneous exposure to space vacuum and extreme UV radiation further decreased the survival of both organisms, compared to unirradiated controls. This is the first report on the isolated effect of extreme UV at 30 nm on cell survival. Extreme UV can only be transmitted through high vacuum, therefore its penetration into the cells may only be superficial, suggesting that in contrast to near UV, membrane proteins rather than DNA were damaged by the radiation. 相似文献
14.
A novel glandular epithelium lining the infrabuccal cavity and anterior pharynx is described in both workers and queens of the pharaoh's ant Monomorium pharaonis. The infrabuccal cavity, connected with the buccal tube, forms a ventral outgrowth of the anterior pharynx, and as such displays the tegumental lining with a cuticle and an epithelial layer. In its dorsal region, the cavity's epithelium reaches a thickness of approx. 11–12 μm in both workers and queens, which is considerably thicker than the epithelium lining the rest of the infrabuccal cavity. Also the possible role of the infrabuccal gland is discussed. 相似文献
15.
Tiia Anmann Rita Guzun Sophie Pelloux Lembi Kogerman Peeter Sikk Nadja Peet Carlos Ojeda Valdur Saks 《BBA》2006,1757(12):1597-1606
The aim of this study was to investigate the mechanism of cellular regulation of mitochondrial respiration in permeabilized cardiac cells with clearly different structural organization: (i) in isolated rat cardiomyocytes with very regular mitochondrial arrangement, (ii) in HL-1 cells from mouse heart, and (iii) in non-beating (NB HL-1 cells) without sarcomeres with irregular and dynamic filamentous mitochondrial network. We found striking differences in the kinetics of respiration regulation by exogenous ADP between these cells: the apparent Km for exogenous ADP was by more than order of magnitude (14 times) lower in the permeabilized non-beating NB HL-1 cells without sarcomeres (25 ± 4 μM) and seven times lower in normally cultured HL-1 cells (47 ± 15 μM) than in permeabilized primary cardiomyocytes (360 ± 51 μM). In the latter cells, treatment with trypsin resulted in dramatic changes in intracellular structure that were associated with 3-fold decrease in apparent Km for ADP in regulation of respiration. In contrast to permeabilized cardiomyocytes, in NB HL-1 cells creatine kinase activity was low and the endogenous ADP fluxes from MgATPases recorded spectrophotometrically by the coupled enzyme assay were not reduced after activation of mitochondrial oxidative phosphorylation by the addition of mitochondrial substrates, showing the absence of ADP channelling in the NB HL-1 cells. While in the permeabilized cardiomyocytes creatine strongly activated mitochondrial respiration even in the presence of powerful competing pyruvate kinase-phosphoenolpyruvate system, in the NB HL-1 cells the stimulatory effect of creatine was not significant. The results of this study show that in normal adult cardiomyocytes and HL-1 cells intracellular local restrictions of diffusion of adenine nucleotides and metabolic feedback regulation of respiration via phosphotransfer networks are different, most probably related to differences in structural organization of these cells. 相似文献
16.
ABSTRACT. The respiration of metamorphosing gyne Lasiusflavus Fab. has been measured in field and laboratory populations. Twelve morphological stages are identified and their respiratory rate investigated. Only five physiological phases are distinguished. The specific respiratory rate varies between these phases, to produce the U-shape characteristic of insects. There is good agreement between the data from English field and Danish laboratory populations. The minimum rate is only 40% of the maximum. Except at the beginning and end of metamorphosis, the Q10 is significantly different in the two temperature intervals 10–20 and 20–30C. Metamorphosis was completed in approximately 33 days at 20 C. The total oxygen consumption by the gynes during metamorphosis was 2.4 ml. Their weight loss amounted to 2.2 mg, or 36% of the dry weight and, of this, 0.67mg was accounted for by fat. Assuming the rest was carbohydrate, consumption of these reserves would release 62.9 J, which, for this combination of fat and carbohydrate, can be calculated to be equivalent to 3.1 ml oxygen which is in reasonable agreement with the figure calculated from the measurement of oxygen consumption. The specific respiratory rate in English field populations of male pupae varies in the same way as the gyne-pupae, but it is about 50% higher. 相似文献
17.
Do Han Kim Young Sup Lee Arthur B. Landry III 《Molecular and cellular biochemistry》1992,114(1-2):105-108
Ca2+ release from skeletal sarcoplasmic reticulum (SR) could be regulated by at least three mechanisms: 1) Ca2+, 2) calmodulin, and 3) Ca2+/calmodulin-dependent phosphorylation. Bell-shaped Ca2+-dependence, of Ca2+ release from both actively- and passively-loaded SR vesicles suggest that opening and closing of the Ca2+ release channel could be regulated by [Ca2+
o] . The time- and concentration-dependent inhibition of Ca 2+ release from skeletal SR by calmodulin was also studied using passively-Ca2+ loaded SR vesicles. Up to 50% of Ca 2+ release was inhibited by calmodulin (0.01–0.5 µM); this inhibition required 5–15 min preincubation time. The hypothesis that Ca2+/calmodulin-dependent phosphorylation of a 60 kDa protein regulates Ca2+ release from skeletal SR was tested by stopped-flow fluorometry using passively-Ca2+-loaded SR vesicles. Approximately 80% of the initial rates of Ca2+-induced Ca2+ release was inhibited by the phosphorylation within 2 min of incubation of the SR with Mg·ATP and calmodulin. We identified two types of 60 kDa phosphoproteins in the rabbit skeletal SR, which was distinguished by solubility of the protein in CHAPS. The CHAPS-soluble 60 kDa phosphoprotein was purified by column chromatography on DEAE-Sephacel, heparin-agarose, and hydroxylapatite. Analyses of the purified protein indicate that the CHAPS-soluble 60 kDa protein is an isoform of phosphoglucomutase (PGM). cDNAs encoding isoforms of PGM were cloned and sequenced using synthetic oligonucleotides. Two types of PGM isoforms (Type I and Type 11) were identified. The translated amino acid sequences show that Type II isoform is SR-form. Our results are significant in terms of understanding evidence of an association of glycolytic and glycogenolytic enzymes with SR and a role in the regulation of SR functions. (Mol Cell Biochem 114: 105-108, 1992) 相似文献
18.
Summary The fine structure of the indirect flight muscles was studied by electron microscopy in the following Notch locus mutants of Drosophila melanogaster reared at 18° C or 29° C for 6 days after eclosion: Ax
16172/Ax16172, Ax28/ Ax28, l(1)Nts1/l(1)Nts1,l(1)Nts1/Y and in wild-type controls. The flies were raised up to eclosion at 25° C or 18° C. It was observed that the l(1)Nts1 flies gradually became flightless within a few days if reared at 29° C as adults, and gross changes in the fine structure of the flight muscles were also observed in flies of this genotype. Peripheral myofilaments of myofibrils were disarranged and the mitochondria diminutive. At 18° C the flight muscles remained normal. In all of the Abruptex (Ax) combinations the flight muscles remained similar to the wild-type controls at both 18° C and 29° C, i.e. they were normal. The results suggest that the Notch gene is active in adult flies in addition to its activity during embryonic, larval and pupal stages, and is directly or indirectly involved in the adult development of the muscle tissue. 相似文献
19.
W. N. Fishbein J. I. Davis J. W. Foellmer 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(3):175-181
The specific activity of three characteristic enzymes, adenylate deaminase, adenylate kinase, and creatine kinase, in the skeletal muscles and heart of a variety of vertebrate land animals, including the human, are surveyed. Data from this study and available studies in the literature suggest that adenosine monophosphate deaminase in land vertebrates is quite high in white skeletal muscle, usually somewhat lower in red muscle, and 15-to 500-fold lower in cardiac muscle. Adenosine monophosphate deaminase is active primarily under ischemic or hypoxic conditions which occur frequently in white muscle, only occasionally in red muscle, and ought never occur in heart muscle, and this may therefore account for observed enzyme levels. The common North American toad, Bufo americanus, provides a striking exception to the rule with cardiac adenosine monophosphate deaminase as high as in mammalian skeletal muscle, whereas its skeletal muscle level of adenosine monophosphate deaminase is several times lower. The exceptional levels in the toad are not due to a change in substrate binding and are not accompanied by comparable change in the level of adenylate or creatine kinase. Nor do they signal any major change in isozyme composition, since a human muscle adenosine monophosphate deaminase-specific antiserum reacts with toad muscle adenosine monophosphate deaminase, but not with toad heart adenosine monophosphate deaminase. They do not represent any general anuran evolutionary strategy, since the bullfrog (Rana catesbeiana) and the giant tropic toad (Bufo marinus) have the usual vertebrate pattern of adenosine monophosphate deaminase distribution. Lower skeletal muscle activities in anurans may simply represent the contribution of tonic muscle fiber bundles containing low levels of adenosine monophosphate deaminase, but the explanation for the extremely high adenosine monophosphate deaminase levels in heart ventricular muscle is not apparent.Abbreviations AK
adenylate kinase
- AMP
adenosine monophosphate
- AMPD, AMP
deaminase
- CPK
creatine (phospho)kinase
- EHNA
erythro-9-(2-hydroxy-3-nonyl)-adenine-HCl 相似文献
20.
Alexandre Dewulf Thibaut De Meulemeester Manuel Dehon Michael S. Engel Denis Michez 《ZooKeys》2014,(389):35-48
Although bees are one of the major lineages of pollinators and are today quite diverse, few well-preserved fossils are available from which to establish the tempo of their diversification/extinction since the Early Cretaceous. Here we present a reassessment of the taxonomic affinities of Melitta willardi
Cockerell 1909, preserved as a compression fossil from the Florissant shales of Colorado, USA. Based on geometric morphometric wing shape analyses M. willardi cannot be confidently assigned to the genus Melitta Kirby (Anthophila, Melittidae). Instead, the species exhibits phenotypic affinity with the subfamily Andreninae (Anthophila, Andrenidae), but does not appear to belong to any of the known genera therein. Accordingly, we describe a new genus, Andrenopteryx
gen. n., based on wing shape as well as additional morphological features and to accommodate M. willardi. The new combination Andrenopteryx willardi (Cockerell) is established. 相似文献