Inhibition by lipoxygenase‐3 ofn‐hexanal generation in soybeans

Abstract

Soybean seeds contain three lipoxygenase isozymes. The functions of these lipoxygenase isozymes in n-hexanal generation were investigated by using mutant lines which lack two or three isozymes. In the presence of linoleic acid. the level of n-hexanal produced was highest in the lipoxygenase-I. -3 double deficient line. follovced by the lipoxygenase-2. -3 double deficient, wild type, and lipoxygenase-I, -2, -3 triple deficient lines in that order, and lowest in the lipoxygenase-l, -2 double deficient line. This suggests that lipoxygenase-3 itself cannot produce the n-hexanal precursor and inhibits the n-hexanal generation through other pathways.n-Hexanal generation; Lipoxygenase: Soybean

Reduction of Off‐Flavor Generation in Soybean Homogenates: A Mathematical Model

“…In the literature, the soybean genotype that consistently produces the most n-hexanal is that which only contains the L-2 isozyme (L 2 ) (Takamura and others 1991; Nishiba and others 1995; Pulvera and others 2006). This is also true of the model.…”

“…Unfortunately, explicit values and K m or V max under similar conditions for L-2 or L-3 were not found in the literature. Takamura and others (1991) gave measurements at pH 6.5 of relative LOX activity for wild-type beans containing all 3 isozymes, and for 3 lines of mutant beans, each only possessing just one of the isozymes. By assuming that the ratios of these results correspond to the relative V max of the 3 LOX isozymes, estimates of the different V max parameters were made.…”

“…This is based on data for the fatty acid composition of typical soybeans given by Liu (1997) and scaled relative to the total protein concentration given by Matoba and others (1985a) of 10 to 20 mg protein/mL. To account for the difference in V max for purified enzyme and for whole bean homogenate, the assumption was made that in wild-type beans L-1, L-2, L-3 are present in similar quantities (Takamura and others 1991) and that each constitutes approximately 1% of total protein (Brash 1999). The final set of V max and K m estimates is given in Table 1.…”

“…The availability of K m and V max kinetic parameters for L-1 and HPL (Bild and others 1977, Matoba and others 1985b), and the relative activity of the 3 LOX isozymes (Takamura and others 1991), leads to the use of a mathematical model with Michaelis–Menten kinetics to simulate the biochemical network of the LOX pathway. Copasi (http://www.copasi.org) is a desktop software application, free for noncommercial use, designed for the modeling of such biochemical networks, and was used to create a deterministic model using a set of ordinary differential equations.…”

“…In particular, studies using various existing soybean strains that lack one or more LOX isozymes show how different soybean genotypes produce different concentrations of n-hexanal following homogenization (Takamura and others 1991; Zhuang and others 1991; Nishiba and others 1995). From some of these studies, kinetic parameters can be derived that can be used to model the biological system mathematically.…”