Página 1 dos resultados de 69975 itens digitais encontrados em 0.033 segundos

Caracterização bioquímica, estrutural e funcional de uma L-aminoácido oxidase isolada de peçonha de Lachesis muta (Serpentes, Viperidae); Purification, biochemistry and functional characterization of a new L-amino acid oxidase from Lachesis muta venom.

Silva, Cristiane Bregge da
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 31/10/2011 PT
Relevância na Pesquisa
671.1748%
As peçonhas de serpentes contêm uma mistura complexa de substâncias farmacologicamente ativas, como metaloproteases, fosfolipases A2, serino-proteases, L-aminoácido oxidase (LAAO), além de outros importantes compostos sem ação enzimática. LAAOs são flavoproteínas que catalisam a desaminação oxidativa de L-aminoácidos e produzem o -cetoácido correspondente, com a concomitante liberação de amônia e peróxido de hidrogênio. A peçonha de Lachesis muta (L. muta) contém L-aminoácido oxidase, a qual pode contribuir com o envenenamento. Portanto, o objetivo deste trabalho é a purificação da L-amino acido oxidase de peçonha de Lachesis muta (LmLAAO) e a sua caracterização bioquímica, estrutural e funcional. Para isso, foram desenvolvidos dois protocolos distintos de purificação, os quais forneceram LmLAAO com grande pureza. No primeiro protocolo, 20 mg de peçonha bruta de L. muta foram submetidos a uma gel filtração em Sephacryl S100®. Das dez frações obtidas, a primeira fração apresentou atividade L-aminoácido oxidase e foi submetida a mais um passo cromatográfico em Mono Q®. A homogeneidade da fração com atividade L-aminoácido oxidase após a troca iônica foi comprovada por presença de banda única com 60...

Antibacterial and antiparasitic effects of Bothrops marajoensis venom and its fractions: Phospholipase A(2) and L-amino acid oxidase

Costa Torres, Alba Fabiola; Dantas, Rodrigo Tavares; Toyama, Marcos H.; Diz Filho, Eduardo; Zara, Fernando Jose; Rodrigues de Queiroz, Maria Goretti; Pinto Nogueira, Nadia Accioly; de Oliveira, Marcia Rosa; Toyama, Daniela de Oliveira; Monteiro, Helena S.
Fonte: Pergamon-Elsevier B.V. Ltd Publicador: Pergamon-Elsevier B.V. Ltd
Tipo: Artigo de Revista Científica Formato: 795-804
ENG
Relevância na Pesquisa
668.63195%
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Some proteins present in snake venom possess enzymatic activities, such as phospholipase A(2) and L-amino acid oxidase. In this study, we verify the action of the Bothrops marajoensis venom (BmarTV), PLA(2) (BmarPLA(2)) and LAAO (BmarLAAO) on strains of bacteria, yeast, and Leishmania sp. The BmarTV was isolated by Protein Pack 5PW, and several fractions were obtained. Reverse phase HPLC showed that BmarPLA(2) was isolated from the venom, and N-terminal amino acid sequencing of sPLA(2) showed high amino acid identity with other lysine K49 sPLA(2)s isolated from Bothrops snakes. The BmarLAAO was purified to high molecular homogeneity and its N-terminal amino acid sequence demonstrated a high degree of amino acid conservation with others LAAOs. BmarLAAO was able to inhibit the growth of P. aeruginosa, C. albicans and S. aureus in a dose-dependent manner. The inhibitory effect was more significant on S. aureus, with a MIC = 50 mu g/mL and MLC = 200 mu g/mL However, the BmarTV and BmarPLA(2) did not demonstrate inhibitory capacity. BmarLAAO was able to inhibit the growth of promastigote forms of L chagasi and L amazonensis, with an IC50 = 2.55 mu g/mL and 2.86 mu g/mL for L. amazonensis and L. chagasi...

Structural insights into selectivity and cofactor binding in snake venom l-amino acid oxidases

Ullah, A.; Souza, T. A C B; Abrego, J. R B; Betzel, C.; Murakami, M. T.; Arni, R. K.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 124-128
ENG
Relevância na Pesquisa
668.62164%
l-Amino acid oxidases (LAAOs) are flavoenzymes that catalytically deaminate l-amino acids to corresponding α-keto acids with the concomitant production of ammonia (NH 3) and hydrogen peroxide (H 2O 2). Particularly, snake venom LAAOs have been attracted much attention due to their diverse clinical and biological effects, interfering on human coagulation factors and being cytotoxic against some pathogenic bacteria and Leishmania ssp. In this work, a new LAAO from Bothrops jararacussu venom (BjsuLAAO) was purified, functionally characterized and its structure determined by X-ray crystallography at 3.1å resolution. BjsuLAAO showed high catalytic specificity for aromatic and aliphatic large side-chain amino acids. Comparative structural analysis with prokaryotic LAAOs, which exhibit low specificity, indicates the importance of the active-site volume in modulating enzyme selectivity. Surprisingly, the flavin adenine dinucleotide (FAD) cofactor was found in a different orientation canonically described for both prokaryotic and eukaryotic LAAOs. In this new conformational state, the adenosyl group is flipped towards the 62-71 loop, being stabilized by several hydrogen-bond interactions, which is equally stable to the classical binding mode. © 2012 Elsevier Inc.

Amino acid composition of parturient plasma, the intervillous space of the placenta and the umbilical vein of term newborn infants

Camelo Jr.,J.S.; Jorge,S.M.; Martinez,F.E.
Fonte: Associação Brasileira de Divulgação Científica Publicador: Associação Brasileira de Divulgação Científica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/05/2004 EN
Relevância na Pesquisa
670.4781%
The objective of the present study was to determine the levels of amino acids in maternal plasma, placental intervillous space and fetal umbilical vein in order to identify the similarities and differences in amino acid levels in these compartments of 15 term newborns from normal pregnancies and deliveries. All amino acids, except tryptophan, were present in at least 186% higher concentrations in the intervillous space than in maternal venous blood, with the difference being statistically significant. This result contradicted the initial hypothesis of the study that the plasma amino acid levels in the placental intervillous space should be similar to those of maternal plasma. When the maternal venous compartment was compared with the umbilical vein, we observed values 103% higher on the fetal side which is compatible with currently accepted mechanisms of active amino acid transport. Amino acid levels of the placental intervillous space were similar to the values of the umbilical vein except for proline, glycine and aspartic acid, whose levels were significantly higher than fetal umbilical vein levels (average 107% higher). The elevated levels of the intervillous space are compatible with syncytiotrophoblast activity, which maintain high concentrations of free amino acids inside syncytiotrophoblast cells...

Amino Acid Metabolic Origin as an Evolutionary Influence on Protein Sequence in Yeast

de Bivort, Benjamin Lovegren; Perlstein, Ethan O.; Kunes, Samuel M.; Schreiber, Stuart L.
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
669.3374%
The metabolic cycle of Saccharomyces cerevisiae consists of alternating oxidative (respiration) and reductive (glycolysis) energy-yielding reactions. The intracellular concentrations of amino acid precursors generated by these reactions oscillate accordingly, attaining maximal concentration during the middle of their respective yeast metabolic cycle phases. Typically, the amino acids themselves are most abundant at the end of their precursor’s phase. We show that this metabolic cycling has likely biased the amino acid composition of proteins across the S. cerevisiae genome. In particular, we observed that the metabolic source of amino acids is the single most important source of variation in the amino acid compositions of functionally related proteins and that this signal appears only in (facultative) organisms using both oxidative and reductive metabolism. Periodically expressed proteins are enriched for amino acids generated in the preceding phase of the metabolic cycle. Proteins expressed during the oxidative phase contain more glycolysis-derived amino acids, whereas proteins expressed during the reductive phase contain more respiration-derived amino acids. Rare amino acids (e.g., tryptophan) are greatly overrepresented or underrepresented...

Impaired nutrient signaling and body weight control in a Na⁺ neutral amino acid cotransporter (Slc6a19)-deficient mouse

Bröer, Angelika; Juelich, Torsten; Vanslambrouck, Jessica M; Tietze, Nadine; Solomon, Peter S; Holst, Jeff; Bailey, Charles G; Rasko, John E J; Bröer, Stefan
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica Formato: 14 pages
Relevância na Pesquisa
670.8514%
Amino acid uptake in the intestine and kidney is mediated by a variety of amino acid transporters. To understand the role of epithelial neutral amino acid uptake in whole body homeostasis, we analyzed mice lacking the apical broad-spectrum neutral (0) amino acid transporter BᴼAT1 (Slc6a19). A general neutral aminoaciduria was observed similar to human Hartnup disorder which is caused by mutations in SLC6A19. Na⁺ -dependent uptake of neutral amino acids into the intestine and renal brush-border membrane vesicles was abolished. No compensatory increase of peptide transport or other neutral amino acid transporters was detected. Mice lacking BᴼAT1 showed a reduced body weight. When adapted to a standard 20% protein diet, BᴼAT1-deficient mice lost body weight rapidly on diets containing 6 or 40% protein. Secretion of insulin in response to food ingestion after fasting was blunted. In the intestine, amino acid signaling to the mammalian target of rapamycin (mTOR) pathway was reduced, whereas the GCN2/ATF4 stress response pathway was activated, indicating amino acid deprivation in epithelial cells. The results demonstrate that epithelial amino acid uptake is essential for optimal growth and body weight regulation.; This work was supported by National Health and Medical Research Council Grant 525415...

Mice lacking neutral amino acid transporter B⁰AT1 (Slc6a19) have elevated levels of FGF21 and GLP-1 and improved glycaemic control

Jiang, Yang; Rose, Adam J.; Sijmonsma, Tjeerd P.; Bröer, Angelika; Pfenninger, Anja; Herzig, Stephan; Schmoll, Dieter; Bröer, Stefan
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
669.7819%
OBJECTIVE: Type 2 diabetes arises from insulin resistance of peripheral tissues followed by dysfunction of β-cells in the pancreas due to metabolic stress. Both depletion and supplementation of neutral amino acids have been discussed as strategies to improve insulin sensitivity. Here we characterise mice lacking the intestinal and renal neutral amino acid transporter B⁰AT1 (Slc6a19) as a model to study the consequences of selective depletion of neutral amino acids. METHODS: Metabolic tests, analysis of metabolite levels and signalling pathways were used to characterise mice lacking the intestinal and renal neutral amino acid transporter B⁰AT1 (Slc6a19). RESULTS: Reduced uptake of neutral amino acids in the intestine and loss of neutral amino acids in the urine causes an overload of amino acids in the lumen of the intestine and reduced systemic amino acid availability. As a result, higher levels of glucagon-like peptide 1 (GLP-1) are produced by the intestine after a meal, while the liver releases the starvation hormone fibroblast growth factor 21 (FGF21). The combination of these hormones generates a metabolic phenotype that is characterised by efficient removal of glucose, particularly by the heart, reduced adipose tissue mass...

Androgen receptor and nutrient signaling pathways coordinate the demand for increased amino acid transport during prostate cancer progression

Wang, Q.; Bailey, C.; Ng, C.; Tiffen, J.; Thoeng, A.; Minhas, V.; Lehman, M.; Hendy, S.; Buchanan, G.; Nelson, C.; Rasko, J.
Fonte: Amer Assoc Cancer Research Publicador: Amer Assoc Cancer Research
Tipo: Artigo de Revista Científica
Publicado em //2011 EN
Relevância na Pesquisa
669.4585%
L-Type amino acid transporters such as LAT1 and LAT3 mediate the uptake of essential amino acids. Here, we report that prostate cancer cells coordinate the expression of LAT1 and LAT3 to maintain sufficient levels of leucine needed for mTORC1 signaling and cell growth. Inhibiting LAT function was sufficient to decrease cell growth and mTORC1 signaling in prostate cancer cells. These cells maintained levels of amino acid influx through androgen receptor-mediated regulation of LAT3 expression and ATF4 regulation of LAT1 expression after amino acid deprivation. These responses remained intact in primary prostate cancer, as indicated by high levels of LAT3 in primary disease, and by increased levels of LAT1 after hormone ablation and in metastatic lesions. Taken together, our results show how prostate cancer cells respond to demands for increased essential amino acids by coordinately activating amino acid transporter pathways vital for tumor outgrowth.; Qian Wang, Charles G. Bailey, Cynthia Ng, Jessamy Tiffen, Annora Thoeng, Vineet Minhas, Melanie L. Lehman, Stephen C. Hendy, Grant Buchanan, Colleen C. Nelson, John E.J. Rasko and Jeff Holst

Characterization of new putative amino acid transporters of the ATF1 superfamily in Arabidopsis thaliana; Charakterisierung der neuen putativen Aminosäuretransporters der ATF1-Überfamilie aus Arabidopsis thaliana

Gonnella, Giorgio
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
EN
Relevância na Pesquisa
670.6249%
The uptake of nitrogen and its translocation in the plant involve the transport of organic nitrogen in the form of amino acids. During the last years, the focus of the studies on amino acid transport in plants moved from biochemical to molecular characterization of the carrier proteins required for this process. Not all the predicted transport fluxes through the membranes of plant cells have already been assigned to a particular carrier protein, although many carrier proteins were functionally characterized. Moreover, many other proteins, whose existence was predicted by genome sequencing and large scale EST projects, were suggested to function as amino acid transporters on the base of sequence similarity and predicted structural features. However, many of such putative transport proteins have not yet been functionally characterized. In this study a group of related Arabidopsis genes encoding putative amino acid transporters have been analyzed in detail. The in silico analysis grouped these genes to the ATF1 superfamily, suggesting a function as amino acid transporters. These proteins have been called AT, for Amino acid Transporters. Attempts to study these proteins by heterologous expression in Saccharomyces cerevisiae and complementation of yeast mutants defective in amino acid uptake...

GC-Content of Synonymous Codons Profoundly Influences Amino Acid Usage

Li, Jing; Zhou, Jun; Wu, Ying; Yang, Sihai; Tian, Dacheng
Fonte: Genetics Society of America Publicador: Genetics Society of America
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
670.0597%
Amino acids typically are encoded by multiple synonymous codons that are not used with the same frequency. Codon usage bias has drawn considerable attention, and several explanations have been offered, including variation in GC-content between species. Focusing on a simple parameter—combined GC proportion of all the synonymous codons for a particular amino acid, termed GCsyn—we try to deepen our understanding of the relationship between GC-content and amino acid/codon usage in more details. We analyzed 65 widely distributed representative species and found a close association between GCsyn, GC-content, and amino acids usage. The overall usages of the four amino acids with the greatest GCsyn and the five amino acids with the lowest GCsyn both vary with the regional GC-content, whereas the usage of the remaining 11 amino acids with intermediate GCsyn is less variable. More interesting, we discovered that codon usage frequencies are nearly constant in regions with similar GC-content. We further quantified the effects of regional GC-content variation (low to high) on amino acid usage and found that GC-content determines the usage variation of amino acids, especially those with extremely high GCsyn, which accounts for 76.7% of the changed GC-content for those regions. Our results suggest that GCsyn correlates with GC-content and has impact on codon/amino acid usage. These findings suggest a novel approach to understanding the role of codon and amino acid usage in shaping genomic architecture and evolutionary patterns of organisms.

GC-Content of Synonymous Codons Profoundly Influences Amino Acid Usage

Li, Jing; Zhou, Jun; Wu, Ying; Yang, Sihai; Tian, Dacheng
Fonte: Genetics Society of America Publicador: Genetics Society of America
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
670.0597%
Amino acids typically are encoded by multiple synonymous codons that are not used with the same frequency. Codon usage bias has drawn considerable attention, and several explanations have been offered, including variation in GC-content between species. Focusing on a simple parameter—combined GC proportion of all the synonymous codons for a particular amino acid, termed GCsyn—we try to deepen our understanding of the relationship between GC-content and amino acid/codon usage in more details. We analyzed 65 widely distributed representative species and found a close association between GCsyn, GC-content, and amino acids usage. The overall usages of the four amino acids with the greatest GCsyn and the five amino acids with the lowest GCsyn both vary with the regional GC-content, whereas the usage of the remaining 11 amino acids with intermediate GCsyn is less variable. More interesting, we discovered that codon usage frequencies are nearly constant in regions with similar GC-content. We further quantified the effects of regional GC-content variation (low to high) on amino acid usage and found that GC-content determines the usage variation of amino acids, especially those with extremely high GCsyn, which accounts for 76.7% of the changed GC-content for those regions. Our results suggest that GCsyn correlates with GC-content and has impact on codon/amino acid usage. These findings suggest a novel approach to understanding the role of codon and amino acid usage in shaping genomic architecture and evolutionary patterns of organisms.

Caracterización de transportadores de aminoácidos en Echinococcus granulosus; Characterization of amino acid transporters from Echinococcus granulosus

Camicia, Federico
Fonte: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires Publicador: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires
Tipo: info:eu-repo/semantics/doctoralThesis; tesis doctoral; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2011 SPA
Relevância na Pesquisa
671.4868%
Echinococcus granulosus es un pequeño parásito cestode cuyo estadío larval causa la equinococcosis quística o hidatidosis. El objetivo de esta tesis fue analizar el transporte de aminoácidos en el estadío de metacestode y diseccionar los componentes moleculares involucrados en el mismo. Los análisis bioinformáticos realizados han mostrado que en Echinococcus spp. los transcriptos codificantes para transportadores de aminoácidos de la familia DAACS (transportadores de aminoácidos/ dicarboxilatos y catión) se encuentran entre los más representados, siendo los transportadores de aminoácidos excitatorios los más expresados dentro de los miembros de esta familia. Los ensayos de transporte efectuados en quistes hidatídicos infértiles indican que la incorporación de glutamato se daría mediante difusión simple, lo cual sugiere que dicho aminoácido podría ser sintetizado endógenamente. Este resultado estaría en concordancia con el hallazgo bioinformático de genes codificantes para enzimas que intervendrían en la síntesis de novo del aminoácido glutamato. Los análisis transcriptómicos sugieren que habría un aumento muy importante en la expresión de transportadores a nivel del parásito adulto con respecto a la forma lavaria...

Amino acid transport across mammalian renal and intestinal epithelia

Broer, Stefan
Fonte: American Physiological Society Publicador: American Physiological Society
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
670.097%
The transport of amino acids in kidney and intestine is critical for the supply of amino acids to all tissues and the homeostasis of plasma amino acid levels. This is illustrated by a number of inherited disorders affecting amino acid transport in epithel

Study on Bacterial Protein Synthesis System toward the Incorporation of D-Amino Acid & Synthesis of 2'-deoxy-3'-mercapto-tRNA

Huang, Po-Yi
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation
EN_US
Relevância na Pesquisa
669.7819%
Life is anti-entropic and highly organized phenomenon with two characteristics reinforcing each other: homochirality and the stereospecific catalysis of chemical reactions. The exclusive presence of L-amino acids and R-sugars in living world well depict this. Hypothetically, the amino acids and sugars of reverse chirality could form a parallel kingdom which is highly orthogonal to the present world. The components from this mirror kingdom, such as protein or nucleic acid, will be much more resistant to the defensive mechanism of present living system, which could be of great value. Therefore, by gradually rewiring the present bio-machineries, we look to build a bridge leading us to the space of mirror-imaged biomolecules. We begin by investigating protein synthesis with mirror amino acid since most amino acids contain one chiral center to be inversed comparing to sugars. In this work, we analyzed three stages critical for the incorporation of D-amino acid into ribosomal protein synthesis: amino acylation, EF-Tu binding of amino acyl-tRNA and delivery bias, and ribosome catalyzed peptidyl transfer. We have demonstrated that the affinity between EF-Tu and amino acyl-tRNA plays critical role on D-amino acid incorporation, and built a platform aimed to select for ribosome tolerating D-amino acid better.; Chemistry and Chemical Biology

The effect of molecular shape on the thermotropic liquid crystal behavior of monolauroylated amino acid glyceride conjugates

Morán, María del Carmen; Pinazo Gassol, Aurora; Clapés Saborit, Pere; Infante, María Rosa; Pons Pons, Ramon
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artículo Formato: 22195 bytes; application/pdf
ENG
Relevância na Pesquisa
669.4596%
10 pages, 6 figures, 5 tables.-- PMID: 16853983 [PubMed].-- Printed version published Nov 8, 2005.; Monoacylglycerol amino acid conjugates constitute a novel class of specific biocompatible surfactants that can be considered analogues to partial glycerides and lysophospholipids. They consist of one aliphatic chain and one polar head, i.e., the amino acid, linked through a glycerol moiety. In a previous work, we synthesized monolauroylated amino acid glyceride conjugates, 1-O-lauroyl-rac-glycero-3-O-(Nα-acetyl-l-amino acid), changing the amino acid headgroup systematically: arginine (compound 2), aspartic acid (compound 3), glutamic acid (compound 4), asparagine (compound 5), glutamine (compound 6), and tyrosine (compound 7), to elucidate the structure−properties relationship governing the occurrence of their polymorphism. The thermotropism of the new compounds was measured with polarizing light microscopy, differential scanning calorimetry, and X-ray diffraction and compared with the classical monoglyceride rac-1-lauroylglycerol (compound 1). The experiments were performed for a sequence of heating, cooling, and reheating scans. The results showed that compounds 1−6 exhibit a thermotropic smectic phase. As a consequence, the substitution of the polar head did not engender any curvature into the system...

"Green" amino acid-based surfactants

Morán, María del Carmen; Pinazo Gassol, Aurora; Pérez, Lourdes; Clapés Saborit, Pere; Angelet, Marta; García Ramón, María Teresa; Vinardell, M. Pilar; Infante, María Rosa
Fonte: Royal Society of Chemistry (Great Britain) Publicador: Royal Society of Chemistry (Great Britain)
Tipo: Artículo Formato: 398711 bytes; application/pdf
ENG
Relevância na Pesquisa
670.8514%
8 pages, 2 figures, 6 schemes, 3 tables.-- Printed version published May 2004.; The value of amino acids and vegetable oil derivatives as raw materials for the preparation of surfactants was recognized as soon as they were discovered early in the last century. Amino acid-based surfactants, which have an amino acid residue as a hydrophilic moiety, are reviewed with respect to their synthesis, properties and some applications. The review covers three main categories of amino acid-based surfactants: N-acyl, N-alkyl amide and O-alkyl ester derivatives among the linear or single chain amino acid-based surfactants; N, N-bis(N-acylarginine),-alkylendiamides, which are gemini amino acid-based surfactants; and 1-monoacyl-rac-glycero-3-O-(N-acetyl-L-amino acid) and 1,2-diacyl-rac-glycero-3-O-(N-acetyl-L-amino acid), both amino acid-based surfactants with glycerolipid-like structures.; This work was supported by the MEC, Projects QUI97-0570 and PPQ2000-1687-CO2-01 and UA-CSIC Interaccion de Tensioactivos con membranas.; Peer reviewed

The orphan transporter v7-3 (slc6a15) is a Na + -dependent neutral amino acid transporter (B 0 AT2)

Broer, Angelika; Tietze, Nadine; Kowalczuk, Sonja; Chubb, Sarah; Kingsland (previously Munzinger), Michael; Bak, Lasse; Broer, Stefan
Fonte: Portland Press Publicador: Portland Press
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
669.0774%
Transporters of the SLC6 (solute carrier 6) family play an important role in the removal of neurotransmitters in brain tissue and in amino acid transport in epithelial cells. In the present study, we demonstrate that mouse v7-3 (slc6a15) encodes a transporter for neutral amino acids. The transporter is functionally and sequence related to B0AT1 (slc6a19) and was hence named B°AT2. Leucine, isoleucine, valine, proline and methionine were recognized by the transporter, with values of K0.5 (half-saturation constant) ranging from 40 to 200 μM. Alanine, glutamine and phenylalanine were low-affinity substrates of the transporter, with K0.5 values in the millimolar range. Transport of neutral amino acids via B0AT2 was Na+-dependent, Cl--independent and electrogenic. Superfusion of mouse B0AT2-expressing oocytes with amino acid substrates generated robust inward currents. Na+-activation kinetics of proline transport and uptake under voltage clamp suggested a 1:1 Na +/amino acid co-transport stoichiometry. Susbtrate and co-substrate influenced each other's K0.5 values, suggesting that they share the same binding site. A mouse B0AT2-like transport activity was detected in synaptosomes and cultured neurons. A potential role of B0AT2 in transporting neurotransmitter precursors and neuromodulators is proposed.

The SLC6 orphans are forming a family of amino acid transporters

Broer, Stefan
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
670.0145%
Transporters in the human genome are grouped in solute carrier families (SLC). The SLC6 family is one of the biggest transporter families in the human genome comprising 20 members. It is usually referred to as the neurotransmitter transporter family because its founding members encode transporters for the neurotransmitters GABA, noradrenaline, serotonin and dopamine. The family also includes a number of 'orphan' transporters, the function of which has remained elusive until recently. Identification of the broadly specific neutral amino acid transporter SLC6A19 (also called B0AT1) suggested that all orphan transporters may in fact be amino acid transporters. This was subsequently confirmed by the identification of SLC6A20 as the long-sought IMINO system, a proline transporter found in kidney, intestine and brain. Very recently, SLC6A15 was identified as the neutral amino acid transporter B0AT2. All amino acid transporters appear to cotransport only 1Na+ together with the amino acid substrate. Both, B0AT1 and B0AT2 are chloride independent, whereas IMINO is chloride dependent. The amino acid transporters of the SLC6 family are functionally and sequence related to the recently crystallized leucine transporter from Aquifex aeolicus. The structure elegantly explains many of the mechanistic features of the SLC6 amino acid transporters.

Adaptation of plasma membrane amino acid transport mechanisms to physiological demands

Broer, Stefan
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
671.4868%
The molecular identification of almost all physiologically characterized amino acid transporters in recent years has facilitated the functional analysis of this important class of transport proteins. The picture that emerges from these studies is that antiport is the prevalent mode of amino acid transport rather than a combination of uniporters and cotransporters. Mainly neurotransmitters and osmolytes are transported by complex cotransport mechanisms that allow a high intracellular accumulation. Antiport mechanisms almost invariably include the nonessential amino acids alanine and glutamine, which are used as exchange substrates. The intracellular level of both amino acids is well regulated by Na+/amino acid cotransporters. Transport mechanisms are not conserved within families and may change with mutation of even a single amino acid residue in the transport protein. Thus transport mechanisms are easily adapted to physiological demands during evolution.

Amino acid Composition of Some Mexican Foods Composición de Aminoácidos en Varios Alimentos Mexicanos

M.C. Morales de León,Josefina; Bourges,Héctor; Q.F.B. Camacho,Ma. Elena¹
Fonte: Sociedad Latinoamericana de Nutrición Publicador: Sociedad Latinoamericana de Nutrición
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2005 EN
Relevância na Pesquisa
670.02375%
Knowledge of the amino acid composition of foods is essential to calculate their chemical score, which is used to predict protein quality of foods and diets. Though amino acid composition of many foods is reasonably well established, better knowledge is needed on native foods consumed in different regions and countries. This paper presents the amino acid composition of different presentations of raw and processed foods produced and consumed in Mexico. The amino acid composition was determined using Beckman amino acid analyzers (models 116 and 6300). Tryptophan was determined using the Spies and Chambers method. Of the different foods analyzed, some comments are made on native or basic foods in Mexico: Spirulin, where lysine is the limiting amino acid, with a chemical score of 67%, is a good source of tryptophan (1.16g/16 gN); amaranth contains high levels of sulphur amino acids (4.09 to 5.34 g/16gN), with a protein content of 15 g/100g; and pulque, a Pre-Hispanic beverage that contains high levels of tryptophan (2.58 g/16 gN) and sulphur amino acids (2.72 g/16 gN). Finally, insects are good sources of sulphur amino acids and lysine.