Influência das enzimas α-galactosidase e poligalacturonase na germinação de sementes de Dalbergia nigra (Leguminoseae- Papilonoidea)

• Autor(a) principal: Pontes, Claudia Aparecida
• Data de Publicação: 2008
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/520
• topic: Enzimas; α-galactosidase; Poligalacturonase; Germinação; Dalbergia nigra; Enzymes; α-galactosidase; Poligalacturonase; Germination; Dalbergia nigra; CNPQ::CIENCIAS AGRARIAS::RECURSOS FLORESTAIS E ENGENHARIA FLORESTAL::SILVICULTURA

This work aimed to study the enzymes α-galactosidase and polygalacturonase and to verify the composition and the alteration of the cell wall sugars and the pectic component in the teguments of D. nigra seeds during the germination. The seeds were submitted to water imbibition for 168 hours. Samples of seeds were taken for the biochemical and kinetic characterization of the enzymes. Activity of the enzyme α- galactosidase increased with the imbibition, although it was not present initially in the embryonic axis of dry seeds. The maximum activity was obtained at ph 5.5 to both compartments. In the cotyledon the activity of the enzyme was higher at temperature of 50°C, and in the embryonic axis it was between 50 and 60°C. The enzyme was tolerant to temperature, but it was not possible to determine its half-life at the temperature of 40 °C, in the period of 10 hours. The activity of the α-galactosidase was inhibited by β- mercaptoethanol and CuSO4 in both compartments, the lactose and the sodium chloride stimulated the activity in the cotyledons and in the embryonic axis. The KM values for the embryonic axis and cotyledons were respectively 0,239 and 0,228 mM. The α-galactosidase is present in the seeds of Dalbergia nigra and its specific activity increases during the germination period. Activity of PG was detected from the first day of imbibition, in the cotyledons and in the embryonic axis. Maximum activity in the cotyledons was detected in the second day and in the axis in the sixth day of soaking. The variation in the proteins content was significant along the time in the cotyledons and in the axis. The activity of PG was maximal at the temperature of 60°C in the cotyledons and in the embryonic axis the maximal activity was observed in a range of temperatures from 55 to 60 °C. The activity of the enzyme was higher at pH 4,0 to all compartments. The KM was 5,08 and 4,39 mM for the cotyledons and axis, respectively. Vmax was 0,026 mM min-1 in the cotyledon enzyme and 0,024 mM min-1 for embryonic axis enzyme. In the teguments, activity of PG was maximal in the third day. The protein content reduced along the imbibition period. The activity of PG was maximal temperatures ranging from 40 to 50 °C. The pH of higher activity to this enzyme was obtained from pH 3 until pH 7,0. The KM and Vmax were 1,34 mM and 0,012 µmol min-1, respectively. It was verified that the galactose is the main component of the pectin, followed by the mannose. Arabinose was the most abundant component in the cell wall, followed by xylose. Based on the results, we can conclude that the enzymes α-galactosidase and PG are acting during the germination of Dalbergia nigra seeds.