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41.
Aminotransferases are essential enzymes involved in the central metabolism of all organisms. The Ialpha subfamily of aspartate and tyrosine aminotransferases (AATases and TATases) is the best-characterized grouping, but only eight enzymes from this subfamily, representing relatively little sequence diversity, have been experimentally characterized for substrate specificity (i.e., AATase vs. TATase). Genome annotation, based on this limited dataset, provides tentative assignments for all sequenced members of this subfamily. This procedure is, however, subject to error, particularly when the experimental basis set is limited. To address this problem we cloned twelve additional subfamily Ialpha enzymes from an evolutionarily divergent set of organisms. Nine were purified to homogeneity after heterologous expression in Escherichia coli in native, intein-tagged or His(6)-tagged forms. The two Saccharomyces cerevisiae isoforms were recombinantly produced in yeast. The effects of the C-terminal tags on expression, purification and enzyme activity are discussed. 相似文献
42.
An intimate interplay exists between the bone and the immune system, which has been recently termed osteoimmunology. The activity
of immune cells affects the intrinsic balance of bone mineralization and resorption carried out by the opposing actions of
osteoblasts and osteoclasts. The aim of this study was to determine the possible interaction between inflammatory-induced
conditions and matrix metalloproteinases-2,-9 (MMP-2,-9) synthesis and secretion by bone marrow-derived osteoprogenitor cells
during advanced stages of osteogenesis. Rat bone marrow-derived mesenchymal stem cells (MSCs) were cultured in the presence
of osteogenic supplements in order to direct the cells towards the osteogenic differentiation lineage. At the late stages
of osteogenesis, assessed by histochemistry, immunohistochemistry and RT-PCR, cultures were exposed to pro-inflammatory cytokines,
tumor necrosis factor-alpha (TNF-α) and interleukin-1alpha (IL-1α). Biochemical, histochemical and molecular biology techniques
were used to discern the influence of pro-inflammatory cytokines on MMP-2,-9 synthesis and secretion. Results indicated that
MMP-9 synthesis and secretion were significantly induced after exposure to the cytokines (TNF-α, IL-1α) treatment, while MMP-2
levels remained unchanged. These results indicate that in response to inflammatory processes, osteoblasts, in addition to
osteoclasts, can also be involved and contribute to the process of active bone resorption by secretion and activation of MMPs. 相似文献
43.
Coregulation of beta-galactoside uptake and hydrolysis by the hyperthermophilic bacterium Thermotoga neapolitana 下载免费PDF全文
Regulation of the beta-galactoside transport system in response to growth substrates in the extremely thermophilic anaerobic bacterium Thermotoga neapolitana was studied with the nonmetabolizable analog methyl-beta-D-thiogalactopyranoside (TMG) as the transport substrate. T. neapolitana cells grown on galactose or lactose accumulated TMG against a concentration gradient in an intracellular free sugar pool that was exchangeable with external galactose or lactose and showed induced levels of beta-galactosidase. Cells grown on glucose, maltose, or galactose plus glucose showed no capacity to accumulate TMG, though these cells carried out active transport of the nonmetabolizable glucose analog 2-deoxy-D-glucose. Glucose neither inhibited TMG uptake nor caused efflux of preaccumulated TMG; rather, glucose promoted TMG uptake by supplying metabolic energy. These data show that beta-D-galactosides are taken up by T. neapolitana via an active transport system that can be induced by galactose or lactose and repressed by glucose but which is not inhibited by glucose. Thus, the phenomenon of catabolite repression is present in T. neapolitana with respect to systems catalyzing both the transport and hydrolysis of beta-D-galactosides, but inducer exclusion and inducer expulsion, mechanisms that regulate permease activity, are not present. Regulation is manifest at the level of synthesis of the beta-galactoside transport system but not in the activity of the system. 相似文献
44.
Substrate specificity characterization for eight putative nudix hydrolases. Evaluation of criteria for substrate identification within the Nudix family 下载免费PDF全文
Vi N. Nguyen Annsea Park Anting Xu John R. Srouji Steven E. Brenner Jack F. Kirsch 《Proteins》2016,84(12):1810-1822
The nearly 50,000 known Nudix proteins have a diverse array of functions, of which the most extensively studied is the catalyzed hydrolysis of aberrant nucleotide triphosphates. The functions of 171 Nudix proteins have been characterized to some degree, although physiological relevance of the assayed activities has not always been conclusively demonstrated. We investigated substrate specificity for eight structurally characterized Nudix proteins, whose functions were unknown. These proteins were screened for hydrolase activity against a 74‐compound library of known Nudix enzyme substrates. We found substrates for four enzymes with kcat/Km values >10,000 M?1 s?1: Q92EH0_LISIN of Listeria innocua serovar 6a against ADP‐ribose, Q5LBB1_BACFN of Bacillus fragilis against 5‐Me‐CTP, and Q0TTC5_CLOP1 and Q0TS82_CLOP1 of Clostridium perfringens against 8‐oxo‐dATP and 3'‐dGTP, respectively. To ascertain whether these identified substrates were physiologically relevant, we surveyed all reported Nudix hydrolytic activities against NTPs. Twenty‐two Nudix enzymes are reported to have activity against canonical NTPs. With a single exception, we find that the reported kcat/Km values exhibited against these canonical substrates are well under 105 M?1 s?1. By contrast, several Nudix enzymes show much larger kcat/Km values (in the range of 105 to >107 M?1 s?1) against noncanonical NTPs. We therefore conclude that hydrolytic activities exhibited by these enzymes against canonical NTPs are not likely their physiological function, but rather the result of unavoidable collateral damage occasioned by the enzymes' inability to distinguish completely between similar substrate structures. Proteins 2016; 84:1810–1822. © 2016 The Authors Proteins: Structure, Function, and Bioinformatics Published by Wiley Periodicals, Inc. 相似文献
45.
The core domain of retrotransposon integrase in Hordeum: predicted structure and evolution 总被引:1,自引:0,他引:1
Suoniemi A; Tanskanen J; Pentikainen O; Johnson MS; Schulman AH 《Molecular biology and evolution》1998,15(9):1135-1144
Propagation of long terminal repeat (LTR)-bearing retrotransposons and
retroviruses requires integrase (IN, EC 2.7.7.-), encoded by the
retroelements themselves, which mediates the insertion of cDNA copies back
into the genome. An active retrotransposon family, BARE-1, comprises
approximately 7% of the barley (Hordeum vulgare subsp. vulgare) genome. We
have generated models for the secondary and tertiary structure of BARE-1 IN
and demonstrate their similarity to structures for human immunodeficiency
virus 1 and avian sarcoma virus INs. The IN core domains were compared for
80 clones from 28 Hordeum accessions representative of the diversity of the
genus. Based on the structural model, variations in the predicted, aligned
translations from these clones would have minimal structural and functional
effects on the encoded enzymes. This indicates that Hordeum retrotransposon
IN has been under purifying selection to maintain a structure typical of
retroviral INs. These represent the first such analyses for plant INs.
相似文献
46.
van Hoek AH; van Alen TA; Sprakel VS; Hackstein JH; Vogels GD 《Molecular biology and evolution》1998,15(9):1195-1206
The 18S and 5.8S rDNA genes and the internal transcribed spacers ITS-1 and
ITS-2 of ciliates living in the hindgut of frogs, millipedes, and
cockroaches were analyzed in order to study the evolution of intestinal
protists. All ciliates studied here belong to the genus Nycrotherus.
Phylogenetic analysis revealed that these ciliates from a monophyletic
group that includes the distantly related anaerobic free-living
heterotrichous ciliates Metopus palaeformis and Metopus contortus. The
intestinal ciliates from the different vertebrate and invertebrate hosts
are clearly divergent at the level of their rDNA repeats. This argues for
the antiquity of the associations and a predominantly vertical
transmission. This mode of transmission seems to be controlled primarily by
the behavior of the host. The different degrees of divergence between
ciliates living in different strains of one and the same cockroach species
most likely reflect the different geographical origins of the hosts. In
addition, host switches must have occurred during the evolution of
cockroaches, since identical ciliates were found only in distantly related
hosts. These phenomena prevent the reconstruction of potential cospeciation
events.
相似文献
47.
48.
Valérie Simonneaux AH Ouichou Cheryl Craft Paul Pévet 《Journal of neurochemistry》1994,62(6):2464-2471
Abstract: Neuropeptide Y is colocalized with noradrena-line in sympathetic fibers innervating the rat pineal gland. In this article we present a study of the effects and mechanisms of action of neuropeptide Y on the pineal noradrenergic transmission, the main input leading to the rhythmic secretion of melatonin. At the presynaptic level, neuropeptide Y inhibits by 45%, with an EC50 of 50 n M , the potassium-evoked noradrenaline release from pineal nerve endings. This neuropeptide Y inhibition occurs via the activation of pertussis toxin-sensitive G protein-coupled neuropeptide Y-Y2 receptors and is independent from, but additive to, the α2 -adrenergic inhibition of noradrenaline release. At the postsynaptic level, neuropeptide Y decreases by a maximum of 35%, with an EC50 of 5 n M , the β-adrenergic induction of cyclic AMP elevation via the activation of neuropeptide Y-Y1 receptors. This moderate neuropeptide Y-induced inhibition of cyclic AMP accumulation, however, has no effect on the melatonin secretion induced by a β-adrenergic stimulation. On the contrary, in the presence of 1 m M ascorbic acid, neuropeptide Y potentiates (up to threefold) the melatonin secretion. In conclusion, this study has demonstrated that neuropeptide Y modulates the noradrenergic transmission in the rat pineal gland at both presynaptic and postsynaptic levels, using different receptor subtypes and transduction pathways. 相似文献
49.
Eman A.E. Badr Abd El-Aleem Hassan Abd El-Aleem Samah EL-Ghlban Asmaa AH. Swelm Mahmoud Emara 《Biochemistry and Biophysics Reports》2019
ObjectivesThe prognosis of high-risk patients might be greatly ameliorated using genetic predisposition risk factors. Sympathetic activity and innate immunity related to neuropeptide Y function may be related to dyslipidemia and atherosclerosis. The aim of this study is to detect the correlation between Neuropeptide Y (NPY) SNP rs16147 and its gene expression in chronic kidney disease with and without hypertension.MethodsThis study carried out on 150 subjects who were divided into 3 main groups group (I) 50 CKD patients with hypertension, group (II) 50 CKD patients without hypertension and group (III) 50 healthy individuals. Carotid intima media thickness (CIMT) was measured by Ultrasound. Kidney function test and lipid profile were performed. Genotyping and gene expression of neuropeptide Y (NPY) were performed using real time PCR.ResultsThere was a significant increase in number and percentage of CC genotype and C allele of NPY SNP distribution in CKD patients with and without hypertension when compared to controls. A significant association was found between CC genotype and C allele and the risk of CKD with hypertension with odd ratio 3.26 and 1.77, respectively. There is a significant positive correlation between NPY gene expression level and CIMT among chronic kidney disease patients with highest level of TC, LDLc and CIMT among CC genotype of NPY gene.ConclusionA significant association was found between CC genotype and C allele of NPY at rs16147 with increase NPY gene expression and risk of developing hypertension in CKD. 相似文献
50.
Rasha AH Attia Abeer E Mahmoud Haiam Mohammed Mahmoud Farrag Rania Makboul Mona Embarek Mohamed Zedan Ibraheim 《Memórias do Instituto Oswaldo Cruz》2015,110(8):1035-1041
Trichinellosis is a serious disease with no satisfactory treatment. We aimed to
assess the effect of myrrh (Commiphora molmol) and, for the first
time, thyme (Thymus vulgaris L.) against enteral
and encysted (parenteral) phases of Trichinella spiralis in mice
compared with albendazole, and detect their effect on inducible nitric oxide synthase
(iNOS) expression. Oral administration of 500 mg/kg of myrrh and thyme led to adult
reduction (90.9%, 79.4%), while 1,000 mg/kg led to larvae reduction (79.6%, 71.3%),
respectively. Administration of 50 mg/kg of albendazole resulted in adult and larvae
reduction (94.2%, 90.9%). Positive immunostaining of inflammatory cells infiltrating
intestinal mucosa and submucosa of all treated groups was detected. Myrrh-treated
mice showed the highest iNOS expression followed by albendazole, then thyme. On the
other hand, both myrrh and thyme-treated groups showed stronger iNOS expression of
inflammatory cells infiltrating and surrounding encapsulated T.
spiralis larvae than albendazole treated group. In conclusion, myrrh and
thyme extracts are highly effective against both phases of T.
spiralis and showed strong iNOS expressions, especially myrrh which could
be a promising alternative drug. This experiment provides a basis for further
exploration of this plant by isolation and retesting the active principles of both
extracts against different stages of T. spiralis. 相似文献