Mostrando recursos 1 - 20 de 27

  1. Hydrolysis of the phosphoanhydride linkage of cyclic ADP-ribose by the Mn2+-dependent ADP-ribose/CDP-alcohol pyrophosphatase

    Canales, José; Fernández, Ascensión; Rodrigues, Joaquim Rui; Ferreira, Rui; Ribeiro, João Meireles; Cabezas, Alicia; Costas, María Jesús; Cameselle, José Carlos
    Cyclic ADP-ribose (cADPR) metabolism in mammals is catalyzed by NAD glycohydrolases (NADases) that, besides forming ADP-ribose, form and hydrolyze the N(1)-glycosidic linkage of cADPR. Thus far, no cADPR phosphohydrolase was known. We tested rat ADP-ribose/CDP-alcohol pyrophosphatase (ADPRibase-Mn) and found that cADPR is an ADPRibase-Mn ligand and substrate. ADPRibase-Mn activity on cADPR was 65-fold less efficient than on ADP-ribose, the best substrate. This is similar to the ADP-ribose/cADPR formation ratio by NADases. The product of cADPR phosphohydrolysis by ADPRibase-Mn was N(1)-(5-phosphoribosyl)-AMP, suggesting a novel route for cADPR turnover.

  2. Bifunctional Homodimeric Triokinase/FMN Cyclase

    Rodrigues, Joaquim Rui; Couto, Ana; Cabezas, Alicia; Pinto, Rosa María; Ribeiro, João Meireles; Canales, José; Costas, María Jesús; Cameselle, José Carlos
    Mammalian triokinase, which phosphorylates exogenous dihydroxyacetone and fructose-derived glyceraldehyde, is neither molecularly identified nor firmly associated to an encoding gene. Human FMN cyclase, which splits FAD and other ribonucleoside diphosphate-X compounds to ribonucleoside monophosphate and cyclic X-phosphodiester, is identical to a DAK-encoded dihydroxyacetone kinase. This bifunctional protein was identified as triokinase. It was modeled as a homodimer of two-domain (K and L) subunits. Active centers lie between K1 and L2 or K2 and L1: dihydroxyacetone binds K and ATP binds L in different subunits too distant (≈ 14 Å) for phosphoryl transfer. FAD docked to the ATP site with ribityl...

  3. Molecular Bases of Catalysis and ADP-Ribose Preference of Human Mn2+-Dependent ADP-Ribose/CDP-Alcohol Diphosphatase and Conversion by Mutagenesis to a Preferential Cyclic ADP-Ribose Phosphohydrolase

    Cabezas, Alicia; Ribeiro, João Meireles; Rodrigues, Joaquim Rui; López-Villamizar, Iralis; Fernández, Ascensión; Canales, José; Pinto, Rosa María; Costas, María Jesús; Cameselle, José Carlos
    Among metallo-dependent phosphatases, ADP-ribose/CDP-alcohol diphosphatases form a protein family (ADPRibase-Mn-like) mainly restricted, in eukaryotes, to vertebrates and plants, with preferential expression, at least in rodents, in immune cells. Rat and zebrafish ADPRibase-Mn, the only biochemically studied, are phosphohydrolases of ADP-ribose and, somewhat less efficiently, of CDP-alcohols and 2´,3´-cAMP. Furthermore, the rat but not the zebrafish enzyme displays a unique phosphohydrolytic activity on cyclic ADP-ribose. The molecular basis of such specificity is unknown. Human ADPRibase-Mn showed similar activities, including cyclic ADP-ribose phosphohydrolase, which seems thus common to mammalian ADPRibase-Mn. Substrate docking on a homology model of human ADPRibase-Mn suggested possible interactions...

  4. Characterization of Danio rerio Mn2+-Dependent ADP-Ribose/CDP-Alcohol Diphosphatase, the Structural Prototype of the ADPRibase-Mn-Like Protein Family

    Rodrigues, Joaquim Rui; Fernández, Ascensión; Canales, José; Cabezas, Alicia; Ribeiro, João Meireles; Costas, María Jesús; Cameselle, José Carlos
    The ADPRibase-Mn-like protein family, that belongs to the metallo-dependent phosphatase superfamily, has different functional and structural prototypes. The functional one is the Mn(2+)-dependent ADP-ribose/CDP-alcohol diphosphatase from Rattus norvegicus, which is essentially inactive with Mg(2+) and active with low micromolar Mn(2+) in the hydrolysis of the phosphoanhydride linkages of ADP-ribose, CDP-alcohols and cyclic ADP-ribose (cADPR) in order of decreasing efficiency. The structural prototype of the family is a Danio rerio protein with a known crystallographic structure but functionally uncharacterized. To estimate the structure-function correlation with the same protein, the activities of zebrafish ADPRibase-Mn were studied. Differences between zebrafish and rat enzymes...

  5. Specific cyclic ADP-ribose phosphohydrolase obtained by mutagenic engineering of Mn2+-dependent ADP-ribose/CDP-alcohol diphosphatase

    Ribeiro, João Meireles; Canales, José; Cabezas, Alicia; Rodrigues, Joaquim Rui; Pinto, Rosa María; López-Villamizar, Iralis; Costas, María Jesús; Cameselle, José Carlos
    Cyclic ADP-ribose (cADPR) is a messenger for Ca2+ mobilization. Its turnover is believed to occur by glycohydrolysis to ADP-ribose. However, ADP-ribose/CDP-alcohol diphosphatase (ADPRibase-Mn) acts as cADPR phosphohydrolase with much lower efficiency than on its major substrates. Recently, we showed that mutagenesis of human ADPRibase-Mn at Phe37, Leu196 and Cys253 alters its specificity: the best substrate of the mutant F37A + L196F + C253A is cADPR by a short difference, Cys253 mutation being essential for cADPR preference. Its proximity to the ‘northern’ ribose of cADPR in docking models indicates Cys253 is a steric constraint for cADPR positioning. Aiming to obtain a specific cADPR phosphohydrolase, new...

  6. Assessing an agri-food development strategy : a bi-regional input–output model with resource-constrained sectors

    Cruz, Luís; Ramos, Pedro N.; Barata, Eduardo; Sargento, Ana Lúcia Marto
    Uneven regional development is widely recognised. This paper explores the effectiveness of a regional development strategy based on the agri-food sector expansion in a laggard agriculture dependent region. We use a bi-regional rectangular Input– Output model, explicitly taking into account the methodological and policy implications of resource-constrained products. Results confirm that local transformation of agricultural products has a positive but limited effect, due to land restrictions and impact leaks to the more complex and developed region. The regional development strategy would be more effective if it focuses instead on non-tradable products or not so dependent on natural resources.

  7. Assessing an agri-food development strategy : a bi-regional input–output model with resource-constrained sectors

    Cruz, Luís; Ramos, Pedro N.; Barata, Eduardo; Sargento, Ana Lúcia Marto
    Uneven regional development is widely recognised. This paper explores the effectiveness of a regional development strategy based on the agri-food sector expansion in a laggard agriculture dependent region. We use a bi-regional rectangular Input– Output model, explicitly taking into account the methodological and policy implications of resource-constrained products. Results confirm that local transformation of agricultural products has a positive but limited effect, due to land restrictions and impact leaks to the more complex and developed region. The regional development strategy would be more effective if it focuses instead on non-tradable products or not so dependent on natural resources.

  8. Comportamento ambiental : estudo comparativo entre estudantes brasileiros e portugueses

    Côrtes, Pedro Luiz; Dias, António Guerner; Fernandes, Maria Eduarda; Pamplona, Jorge Manuel
    Jovens universitários têm acesso crescente às informações ambientais, mas isso não significa que haja o desenvolvimento de um comportamento em prol do meio ambiente. Com a utilização de uma escala aplicada em 1035 estudantes universitários do Brasil e de Portugal, foi averiguado como ocorre a estruturação e manifestação do comportamento ambiental desses estudantes. Utilizando técnicas estatísticas multivariadas, verificou-se uma similaridade no comportamento ambiental de ambos os grupos, com as crenças ambientais se manifestando por uma oposição à visão antropocêntrica. As atitudes ambientais têm como antecedentes as preocupações relacionadas ao meio ambiente. Essas preocupações influem na opção pelo controle do crescimento...

  9. Comportamento ambiental : estudo comparativo entre estudantes brasileiros e portugueses

    Côrtes, Pedro Luiz; Dias, António Guerner; Fernandes, Maria Eduarda; Pamplona, Jorge Manuel
    Jovens universitários têm acesso crescente às informações ambientais, mas isso não significa que haja o desenvolvimento de um comportamento em prol do meio ambiente. Com a utilização de uma escala aplicada em 1035 estudantes universitários do Brasil e de Portugal, foi averiguado como ocorre a estruturação e manifestação do comportamento ambiental desses estudantes. Utilizando técnicas estatísticas multivariadas, verificou-se uma similaridade no comportamento ambiental de ambos os grupos, com as crenças ambientais se manifestando por uma oposição à visão antropocêntrica. As atitudes ambientais têm como antecedentes as preocupações relacionadas ao meio ambiente. Essas preocupações influem na opção pelo controle do crescimento...

  10. The impact of capital structure on abnormal return: does family control impact?

    Lisboa, Inês
    Purpose: This study analyses the impact of family control in the relationship between abnormal returns and gearing for Portuguese listed firms. Moreover, it provides new evidence on this field taking into account firms’ heterogeneities, namely size effect. Design/methodology/approach: This paper uses a panel data of Portuguese listed firms with different capital structure and various industries. The sample period is from 1999 to 2012. Findings: The models results show that size effect causes inference on results. To small-size firms, abnormal return declines with firm’s gearing, but it increases with market gearing to large-size firms. To the overall sample firm’s gearing in insignificant in...

  11. The impact of capital structure on abnormal return: does family control impact?

    Lisboa, Inês
    Purpose: This study analyses the impact of family control in the relationship between abnormal returns and gearing for Portuguese listed firms. Moreover, it provides new evidence on this field taking into account firms’ heterogeneities, namely size effect. Design/methodology/approach: This paper uses a panel data of Portuguese listed firms with different capital structure and various industries. The sample period is from 1999 to 2012. Findings: The models results show that size effect causes inference on results. To small-size firms, abnormal return declines with firm’s gearing, but it increases with market gearing to large-size firms. To the overall sample firm’s gearing in insignificant in...

  12. Impact of financial crisis and family control on earnings management of Portuguese listed firms

    Lisboa, Inês
    Accounting information is used to evaluate the firm’s financial performance. Although, firms may have incentives to engage in earnings management, misleading all stakeholders. This study aims to analyse earnings management behaviours of Portuguese listed firms. Both accrual-based and real activities of earnings management are analysed to draw an overall picture of earnings management’ strategies. Most studies focused only in discretionary accruals as a proxy for earnings management, since cash flow-based earnings management is more difficult to detect. Although both strategies can be complementary instead of substituting. Moreover, the impact of financial crisis, family control, and firm characteristics is taken into account....

  13. Impact of financial crisis and family control on earnings management of Portuguese listed firms

    Lisboa, Inês
    Accounting information is used to evaluate the firm’s financial performance. Although, firms may have incentives to engage in earnings management, misleading all stakeholders. This study aims to analyse earnings management behaviours of Portuguese listed firms. Both accrual-based and real activities of earnings management are analysed to draw an overall picture of earnings management’ strategies. Most studies focused only in discretionary accruals as a proxy for earnings management, since cash flow-based earnings management is more difficult to detect. Although both strategies can be complementary instead of substituting. Moreover, the impact of financial crisis, family control, and firm characteristics is taken into account....

  14. Capital structure of exporter SMEs during the financial crisis: evidence from Portugal

    Lisboa, Inês
    This study aims to identify the most important determinants to explain the capital structure of exporter SMEs during the financial crisis. Capital structure is measured using three alternative ratios: total debt, long-term debt, and short-term debt, as the impact of the determinants can depend on debt maturity. Analysing an unbalanced sample of 277 Portuguese exporter SMEs, from 2008 until 2014, and using a panel data methodology, estimating the models with fixed effects for firms, the results suggest that size, profitability, asset structure, non-debt tax shields, growth, liquidity, and age are important determinants for explaining firms’ capital structure. Furthermore, exports intensity...

  15. Capital structure of exporter SMEs during the financial crisis: evidence from Portugal

    Lisboa, Inês
    This study aims to identify the most important determinants to explain the capital structure of exporter SMEs during the financial crisis. Capital structure is measured using three alternative ratios: total debt, long-term debt, and short-term debt, as the impact of the determinants can depend on debt maturity. Analysing an unbalanced sample of 277 Portuguese exporter SMEs, from 2008 until 2014, and using a panel data methodology, estimating the models with fixed effects for firms, the results suggest that size, profitability, asset structure, non-debt tax shields, growth, liquidity, and age are important determinants for explaining firms’ capital structure. Furthermore, exports intensity...

  16. O Programa Revitalizar diminui o risco de falência?

    Lisboa, Inês; Gregório, Carina
    Objetivo: O objetivo do presente estudo é verificar Programa Revitalizar, a probabilidade de falência das empresas que recorreram ao mesmo diminuiu. Metodologia: São analisadas as empresas que recorreram ao Programa Revitalizar no ano de 2012. É depois analisada a probabilidade de falência recorrendo ao modelo de Altman na sua versão normal (1993) e na sua versão ajustada. Resultados: Os principais resultados evidenciam que, de modo geral, as empresas da amostra melhoraram os seus resultados após a entrada no Programa Revitalizar, validando a relevância do mesmo. Ajustando o modelo de Altman à amostra em questão constata-se que as variáveis mais relevantes para prever...

  17. O Programa Revitalizar diminui o risco de falência?

    Lisboa, Inês; Gregório, Carina
    Objetivo: O objetivo do presente estudo é verificar Programa Revitalizar, a probabilidade de falência das empresas que recorreram ao mesmo diminuiu. Metodologia: São analisadas as empresas que recorreram ao Programa Revitalizar no ano de 2012. É depois analisada a probabilidade de falência recorrendo ao modelo de Altman na sua versão normal (1993) e na sua versão ajustada. Resultados: Os principais resultados evidenciam que, de modo geral, as empresas da amostra melhoraram os seus resultados após a entrada no Programa Revitalizar, validando a relevância do mesmo. Ajustando o modelo de Altman à amostra em questão constata-se que as variáveis mais relevantes para prever...

  18. Input-output modelling based on total-use rectangular tables: is this a better way?

    Sargento, Ana; Ramos, Pedro; Hewings, Geoffrey
    Input-output tables can be presented in different formats, according to three main criteria: 1) symmetric or rectangular format; 2) total or domestic-use flows and 3) valuation prices (basic prices – bp or purchasers’ prices – pp). Official National Accounts (at least in EU) produce in a regular base a total use rectangular table at pp – also known as the Make and Use (M&U) format – that is different from the lay-out upon which traditional input-output models were developed (domestic use, symmetric, bp). The problem with this latter one is of course that it is only available at times in...

  19. Input-output modelling based on total-use rectangular tables: is this a better way?

    Sargento, Ana Lúcia Marto; Ramos, Pedro; Hewings, Geoffrey
    Input-output tables can be presented in different formats, according to three main criteria: 1) symmetric or rectangular format; 2) total or domestic-use flows and 3) valuation prices (basic prices – bp or purchasers’ prices – pp). Official National Accounts (at least in EU) produce in a regular base a total use rectangular table at pp – also known as the Make and Use (M&U) format – that is different from the lay-out upon which traditional input-output models were developed (domestic use, symmetric, bp). The problem with this latter one is of course that it is only available at times in...

  20. The inclusion of the other in ourselves: reception and comprehension of refugees in Portugal

    Vieira, Ana Maria; Marques, José Carlos; Gomes, Miguel Prata; Vieira, Ricardo
    info:eu-repo/semantics/publishedVersion

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