Mércia Melo de Almeida

Vanadium haloperoxidases from brown algae of the Laminariaceae family.

Vanadium haloperoxidases were extracted, purified and characterized from three different species of Laminariaceae--Laminaria saccharina (Linné) Lamouroux, Laminaria hyperborea (Gunner) Foslie and Laminaria ochroleuca de la Pylaie. Two different forms of the vanadium haloperoxidases were purified from L. saccharina and L. hyperborea and one form from L. ochroleuca species. Reconstitution experiments in the presence of several metal ions showed that only vanadium(V) completely restored the enzymes activity. The stability of some enzymes in mixtures of buffer solution and several organic solvents such as acetone, ethanol, methanol and 1-propanol was noteworthy; for instance, after 30 days at least 40% of the initial activity for some isoforms remained in mixtures of 3:1 buffer solution/organic solvent. The enzymes were also moderately thermostable, keeping full activity up to 40 degrees C. Some preliminary steady-state kinetic studies were performed and apparent Michaelis-Menten kinetic parameters were determined for the substrates iodide and hydrogen peroxide. Histochemical studies were also performed in fresh tissue sections from stipe and blade of L. hyperborea and L. saccharina, showing that haloperoxidase activity was concentrated in the external cortex near the cuticle, although some activity was also observed in the inner cortical region.

Saccorhiza polyschides (phaeophyceae; phyllariaceae) A new source for vanadium-dependent haloperoxidases

Abstract Vanadium-dependent iodoperoxidases from the brown seaweed Saccorhiza polyschides (Lightfoot) Batters, collected at three different locations along the Portuguese west coast, were extracted, purified and characterized. Several extraction procedures were tested, including two-phase aqueous systems. The purification of the iodoperoxidases was achieved using hydrophobic interaction chromatography followed by chromatofocusing. It was possible to isolate three different isoforms of the enzyme, which show mainly iodoperoxidase activity. The three native enzymes have a relative M r around 125 kDa, and two subunits of M r about 64 kDa. Reactivation studies of the apoenzymes with several metal ions revealed that vanadium(V) was essential for enzymatic activity. These enzymes are remarkably thermostable, maintaining their maximum activity up to 50°. The kinetic parameters for the enzyme catalysed iodoperoxidase reaction were obtained at pH 6.1. In the concentration range studied (0.2–8 mM) there was no inhibition by H 2 O 2 whereas iodide inhibition was already apparent at the top values of the concentration range studied (2–25 mM).

Cinética da produção do fermentado alcoólico de abacaxi ‘pérola’ e caracterização da bebida

O pinhao-manso (Jatropha curcas L.) e uma planta oleaginosa, da familia das euforbiaceas, nativa das Americas e, atualmente, considerada uma alternativa para producao de biodiesel, exigente a insolacao e resistente a seca. Nesta pesquisa, os estudos foram voltados para a avaliacao do desenvolvimento da cultura do pinhao-manso, testando tecnicas de plantio que contribuem para maior eficiencia de captacao de agua de chuvas in situ. O experimento foi desenvolvido nas instalacoes da Estacao Experimental do Instituto Nacional do Semiarido - INSA, localizada no municipio de Campina Grande-PB. O delineamento estatistico utilizado foi em blocos casualizados, com tres repeticoes, sendo estudados cinco tecnicas de captacao de agua in situ. Ao longo do ciclo as variaveis de crescimento sao beneficiadas pelas formas de preparacao do solo, para favorecer a captacao de agua in situ, em comparacao ao tratamento com ausencia de tecnica de captacao.