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Previous issue date: 2014-08-28 === Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES === Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico - CNPq === O metabolismo vegetal ? composto por uma complexa rede de eventos f?sicos e qu?micos que
resultam na fotoss?ntese, respira??o, e na s?ntese e degrada??o de compostos org?nicos. Isto
s? ? poss?vel gra?as aos diferentes tipos de respostas a in?meras varia??es ambientais que
um vegetal pode estar sujeito, adquiridas ao longo da evolu??o, levando tamb?m a conquistas
de novos ambientes. O ciclo do glioxilato ? uma via metab?lica localizada nos glioxissomos
de plantas, que possui papel ?nico no estabelecimento das pl?ntulas. Considerado como uma
varia??o do ciclo do ?cido c?trico esta via utiliza uma mol?cula de acetil-Coenzima A, oriunda
da beta-oxida??o de lip?dios para sintetizar compostos que s?o utilizados na s?ntese de
carboidratos. As enzimas Malato sintase (MLS) e Isocitrato liase (ICL) s?o exclusivas deste
ciclo e essenciais na regula??o da bioss?ntese de carboidratos. Devido ? aus?ncia das etapas
de descarboxila??o, como fatores limitantes da velocidade, estudos mais detalhados da
filogenia e evolu??o molecular dessas prote?nas permite o esclarecimento dos efeitos da
presen?a desta rota nos processos evolutivos envolvidos em esp?cies vegetais. Portanto, o
objetivo deste trabalho foi estudar a rela??o entre a evolu??o molecular das enzimas Isocitrato
liase e Malato sintase e sua filogenia, nas plantas verdes (Viridiplantae). Para isso, foram
utilizadas sequ?ncias de amino?cidos e nucleot?deos dos genes, a partir de reposit?rios online
como o Genbank e Uniprot. As sequ?ncias foram alinhadas e, em seguida, submetidos ?
an?lise estat?stica dos modelos de melhor ajuste de substitui??o. A filogenia foi reconstru?da
por m?todos de dist?ncia (Neighbor-joining) e m?todos discretos (M?xima Verossimilhan?a,
M?xima Parcim?nia e An?lise Bayesiana). O reconhecimento de padr?es estruturais na
evolu??o das enzimas foi feito por predi??o e modelagem por homologia das estruturas das
sequ?ncias das prote?nas obtidas. Com base nas an?lises comparativas entre modelos in
silico, das enzimas, e partir dos resultados de infer?ncia filogen?tica, ambas as enzimas
apresentam um padr?o de conserva??o relativamente elevado em sua estrutura e geram
topologias condizentes com dois processos de sele??o e especializa??o dos seus respectivos
genes. Deste modo, confirmando a relev?ncia em se realizar novos estudos para se elucidar
o metabolismo vegetal sob uma perspectiva evolutiva das rela??es entre os genes e a
express?o de suas enzimas === The plant metabolism consists of a complex network of physical and chemical events resulting
in photosynthesis, respiration, synthesis and degradation of organic compounds. This is only
possible due to the different kinds of responses to many environmental variations that a plant
could be subject through evolution, leading also to conquering new surroundings. The
glyoxylate cycle is a metabolic pathway found in glyoxysomes plant, which has unique role in
the seedling establishment. Considered as a variation of the citric acid cycle, it uses an acetyl
coenzyme A molecule, derived from lipids beta-oxidation to synthesize compounds which are
used in carbohydrate synthesis. The Malate synthase (MLS) and Isocitrate lyase (ICL) enzyme
of this cycle are unique and essential in regulating the biosynthesis of carbohydrates. Because
of the absence of decarboxylation steps as rate-limiting steps, detailed studies of molecular
phylogeny and evolution of these proteins enables the elucidation of the effects of this route
presence in the evolutionary processes involved in their distribution across the genome from
different plant species. Therefore, the aim of this study was to establish a relationship between
the molecular evolution of the characteristics of enzymes from the glyoxylate cycle (isocitrate
lyase and malate synthase) and their molecular phylogeny, among green plants (Viridiplantae).
For this, amino acid and nucleotide sequences were used, from online repositories as UniProt
and Genbank. Sequences were aligned and then subjected to an analysis of the best-fit
substitution models. The phylogeny was rebuilt by distance methods (neighbor-joining) and
discrete methods (maximum likelihood, maximum parsimony and Bayesian analysis). The
identification of structural patterns in the evolution of the enzymes was made through homology
modeling and structure prediction from protein sequences. Based on comparative analyzes of
in silico models and from the results of phylogenetic inferences, both enzymes show significant
structure conservation and their topologies in agreement with two processes of selection and
specialization of the genes. Thus, confirming the relevance of new studies to elucidate the
plant metabolism from an evolutionary perspective
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