Efeito do inibidor de protease Kunitz sobre níveis de lipoxigenases em sementes de soja

Abstract

RESUMOAs lipoxigenases (LOX) são responsáveis pelo beany flavor , sabor característico da soja [Glycine max. (L.) Merrill], que é o maior obstáculo ao consumo da soja nos países ocidentais. O inibidor de tripsina Kunitz (KTI) é responsável por 80% da inibição da atividade tríptica, além de provocar hiperplasia pancreática em animais monogástricos. Essas duas características são muito importantes em programas de melhoramento que visam à melhoria da qualidade da soja. Objetivou-se, neste trabalho verificar o efeito do inibidor de protease (KTI), sobre níveis de LOX em sementes de soja, nos seguintes genótipos: KTI+/LOX+, KTI+/LOX-, KTI-/LOX+ e KTI-/LOX-. As LOXs foram identificadas por teste colorimétrico, atividade enzimática e eletroforese em gel de poliacrilamida. O teor de proteína foi quantificado pelo método do ácido bicinconínico para determinação da atividade específica de LOX. Observouse que, para o genótipo KTI+/LOX+, a atividade específica de LOX 1 foi alta, variando de 177,92 a 206,94 UA/mg de proteína e para LOX 3 variou de 17,90 a 19,85 UA/mg de proteína; para KTI+/LOX-e KTI-/LOX-não foi detectada atividade de LOX e que para o genótipo KTI-/LOX+ a atividade específica para LOX 1 variou de 117,24 a 124,64 UA/mg de proteína, e de 17,35 a 20,29 UA/mg de proteína para LOX 3. Houve uma redução de 40% na atividade específica de LOX1 e de 1% para LOX 3, no genótipo KTI-/LOX+, quando comparados ao KTI+/LOX+. Esses resultados comprovam uma associação negativa entre o inibidor de tripsina Kunitz e a atividade de lipoxigenases. Termos para indexação:Glycine max, tripsina, proteína, atividade enzimática, KTI. ABSTRACTLipoxygenases (LOX) are responsible for the beany flavor, which is the most important obstacle for the consumption of soybean [Glycine max. (L.) Merrill] products in Western countries. The Kunitz trypsin inhibitor (KTI) is responsible for 80% of the inhibition of tryptic activity in soybean seeds, and besides it can cause pancreatic hyperplasia in monogastric animals. These two traits are very important in soybean breeding programs that aim the improvement of soy protein quality. The objective of this study was to verify the influence of KTI on LOX levels in soybean seeds by analyzing the following genotypes: KTI+/LOX+, KTI+/LOX-, KTI-/ LOX+ and KTI-/LOX-. LOX 1 and LOX 3 were identified by colorimetric, activity and electrophoretic assays. There was a reduction of 40% on LOX 1 specific activity and 1% for LOX 3 in the KTI-/LOX+ genotype in comparison to genotype KTI+/LOX+. These results indicate an inverse relationship between the presence of the Kunitz trypsin inhibitor in soybean seeds and lipoxygenase activity.

Kunitz trypsin Inhibitor and phytic acid levels in conventional and genetically modified soybean seeds from Londrina and Ponta Grossa, South Brazil

“…Protease inhibitors, constituting one of the soybean protein fractions, represent approximately 6.0% of all existing proteins (BRANDON et al, 1993;MANDARINO, 2010). The presence of these inhibitors in soy-based foods and dietetic products may cause pancreatic nodular hyperplasia in monogastric animals, as shown by studies with guinea pigs (BARROS et al, 2008). In soybeans, two different protease inhibitors can be found -chymotrypsin, also called the Bowman-Birk inhibitor (BBI), and trypsin, known as the Kunitz trypsin inhibitor (KTI) (STAHLHUT; HYMOWITZ, 1983;MANDARINO, 2010).…”

Contribution of the universities to the development of field crop cultivars

“…In the 1980s, UFV included in the objectives of its breeding program the quality improvement of soybeans for human consumption, including better taste, levels of oil and protein, elimination of antinutritional factors, reduction of polysaccharides, altered levels of unsaturated fatty acids and others (Pereira et al 1992, Araújo et al 1997, Moreira et al 1997, Utumi et al 1998, Chiari et al 2004, Lanna et al 2005, Sediyama et al 2005, Moraes et al 2006, Barros et al 2008, Teixeira et al 2012. Simultaneously, the use of biotechnology tools became part of the routine in the work of soybean breeding (Alzate-Marin et al 1996, Moreira et al 1997, Schuster et al 2001, Moraes et al 2006.…”

Nutritional and Bioactive Compounds of Soybean: Benefits on Human Health

“…There are two types of inhibitors: the Kunitz trypsin (KTI), and trypsin inhibitor and chymotrypsin Browman-Birk (BBI) (Miura et al, 2005;Monteiro et al, 2004;Monteiro et al, 2003). Although cultivars without protease inhibitors already exist (Barros et al, 2008), heat treatment alone is able to inactivate them, improving its nutritional value (Miura et al, 2005). These compounds can be removed with heat treatment of the grain and genetic breeding, without prejudice the quality of protein (Andrade et al, 2010;Machado et al, 2008).…”