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URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11847
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Item Efeito da aplicação foliar de ácidos graxos na "via das lipoxigenases" de plantas de soja(Química Nova, 2002-11) Batista, Rosa Bárbara; Oliveira, Maria Goreti de Almeida; Pires, Christiano Vieira; Lanna, Anna Cristina; Gomes, Maria Regina Araújo; José, Inês Chamel; Piovesan, Newton Deniz; Rezende, Sebastião Tavares de; Moreira, Maurilio AlvesThe involvement of lipoxygenase isozymes in several physiological processes of plants has been described but their role is not well understood and more biochemical studies are needed to elucidate the role of the "Lipoxygenase Pathway" in plant physiology. Thus, the biochemical and kinetic characterization of a lipoxygenases "pool" from soybean leaves was carried out. Two genotypes were used: IAC-100 (a normal variety having lipoxygenases in the seeds) and IAC-100 TN (genetically modified genotype, which is devoid of lipoxygenases in the seeds). The plants were submitted to the application of fatty acids (lipoxygenase substrates) on leaves. The results of the biochemical and kinetic studies of lipoxygenase isozymes from leaves of the two genotypes analysed showed that genetic removal of lipoxygenase from seeds did not affect the response of the plant to the treatment, since both genotypes showed similar results.Item Biochemical properties of soybean leaf lipoxygenases: Presence of soluble and membrane-bound forms(Plant Physiology and Biochemistry, 2001-02) Baracat-Pereira, Maria Cristina; Oliveira, Maria Goreti de Almeida; Barros, Everaldo Gonçalves de; Moreira, Maurílio Alves; Santoro, Marcelo MatosLipoxygenases (EC 1.13.11.12, LOX) extracted from soybean leaves (Glycine max [L.] Merrill cv. IAC-100) at pH 6.5 showed low stability. Given the importance of correlating the biochemical roles with the physiological characteristics of each LOX isoenzyme, this work evaluates biochemical characteristics and stability conditions of these enzymes in order to plan a purification procedure. LOX activity (A234 at pH 6.0) increased four to five times when 0.25 % (v/v) Triton X-100, 1 % (w/v) polyvinylpyrrolidone, and 1 mM phenylmethylsulfonyl fluoride were added to leaf macerates. Fe2+ (1 mM) stabilised LOX (70.3 % of activity recovered after 48 h storage). Ammonium sulphate fractionation (35–65 % saturation) increased specific LOX activity five times and stabilised the enzymes. Two optimum LOX activities were observed at pH 6.0–6.5 and 4.0–5.0, and the greater storage stability was at pH 6.5 (after 24–28 h storage at different pH values). The results suggest the presence of at least two different forms of the enzyme. The forms of LOX that are active at acidic pH are more stable than the ones that are active at neutral pH. These stable forms were extracted in absence of detergents (soluble forms), while the forms of LOX that are active at pH 6.0–6.5 are unstable forms specially extracted in presence of Triton X-100, and possibly correspond to membrane-bound proteins.