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Aminocetone oxidase from Stretococcus oligofermentas belongs to a new three-domain family of bacterial flavoproteins
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Characterization of the human D-amino acid oxidase (hDAAO) - pLG72 complex involved in the onset of schizophrenia.
No full textSchizophrenia is a chronic and severely debilitating psychiatric disorder affecting nearly 1% of the world’s population. In 2002, the new human gene G72, encoding for the pLG72 protein, and the gene encoding for DAAO have been genetically linked to the susceptibility to schizophrenia. A yeast two-hybrid screening experiment identified D-amino acid oxidase (DAAO) as a putative interacting partner of pLG72. DAAO is a FAD-containing flavooxidase that in brain is responsible for the elimination of D-serine, a co-agonist that binds to the glycine-site of the NMDA receptor. We recently demonstrated that pLG72 acts as “inactivator” of human DAAO and that the cellular concentration of D-serine depends on the expression of the active form of this flavooxidase. Based on these results, a molecular model for the onset of schizophrenia has been proposed: a decrease in pLG72 expression might yield an anomalous high level of hDAAO activity and therefore a decrease in the local concentration of D-serine, affecting glutamatergic neurotransmission mediated by NMDA receptor.
The characterization of the complex is a challenging task, hardly feasible by high resolution techniques, since: 1) structural informations on pLG72 are lacking; 2) pLG72 is soluble only in the presence of mild denaturant; 3) no homologous protein has been structurally characterized so far. In this perspective, we have used low resolution strategies based on the coupling of classical biochemistry approaches (complementary proteolysis, cross-link) with mass spectrometric techniques, to characterize the pLG72-hDAAO complex. Results indicated that hDAAO exhibits different proteolysis profiles when isolated or in complex with pLG72, thus suggesting a conformational change upon binding the effector protein. Chemical cross-linking experiments will complement the proteolysis experiments providing with details the contact regions between hDAAO e pLG72
Breaking lignin: blue and yellow laccases for a green chemistry
No full textLignin is an amorphous polymer with a molecular mass around 10 kDa that presents a three-dimensional structure disordered and branched, insoluble in water and most common solvents. During the industrial processes, lignin must be degraded and effectively removed. Enzymatic hydrolysis could be an environmentally friendly alternative to chemical methods to perform lignin degradation. The identification of enzymes able to efficiently fragmenting lignin, i.e., an "enzymatic tool box", is of utmost importance. On this side, laccase represents an enzymatic class of main relevance.
Laccases are attracting great scientific interest because of their very basic requirements and huge catalytic capabilities: this renders it one of the ‘‘greenest’’ enzymes [1].
In order to identify interesting lignin degrading biocatalysts, in this study we evaluated the main biochemical properties of a number of commercial and recombinant laccases under identical experimental conditions. The kinetic properties of laccases has been determined on 3 substrates: ABTS, catechol and 2,6-dimethoxyphenol (2,6-DMP). The microbial Bacillus licheniformis laccase (BALL) showed the highest specific activity and catalytic efficiency on ABTS, while the recombinant OB1 from Basidiomycete PM-1 showed the highest affinity for this compound [2]. The stability on pH, temperature, detergents and DMSO of the different laccases was also assessed.
Finally, a change in MW distribution after incubation of lignin with the laccase from Trametes versicolor was observed in gel permeation chromatography.
This work was done as part of the ValorPlus project that has received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no FP7-KBBE-2013-7-613802.
[1] L. Pollegioni, F. Tonin, E. Rosini, FEBS J. 282 (7) (2015) 1190-1213
[2] F. Tonin, R. Melis, A. Cordes, A. Sanchez-Amat, L. Pollegioni, E. Rosini, Submitte
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
The primary structure of D-amino acid oxidase from Rhodotorula gracilis
No full textThe amino acid sequence of D-amino acid oxidase from Rhodotorula gracilis was determined by automated Edman degradation of peptides generated by enzymatic and chemical cleavage. The enzyme monomer contains 368 amino acid residues and its sequence is homologous to that of other known D-amino acid oxidases. Six highly conserved regions appear to have a specific role in binding of coenzyme FAD, in active site topology and in peroxisomal targeting. Moreover, Rhodotorula gracilis D-amino acid oxidase contains a region with a cluster of basic amino acids, probably exposed to solvent, which is absent in other D-amino acid oxidases
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