Distribution of Peroxidases in Durum Wheat (Triticum durum)

Abstract

Cereal Chem. 77(1): [11][12][13][14][15][16][17] A biochemical study of the main durum wheat milling fractions (bran, embryo, and semolina) showed that peroxidases (POD) were present in multiple forms in the kernel and appeared to be tissue specific: one form for the embryo, one for the endosperm, one for the subaleuronic layer, and one for the outer layers. Large varietal differences were found regarding both the composition and the POD activity. POD activity, detected by diaminobenzidine, was found mainly in the cell wall of the subaleurone layer and inside some specific, differentiated cells of the embryo. Immunolocalization with antibodies of durum wheat POD showed the presence of POD in several layers of the pericarp (epidermis) and the seed coat (testa), in the embryo, and also in the endosperm. In this latter tissue, the staining intensity decreased gradually from the outer layers toward the center of the kernel. The localization of POD in durum wheat kernel suggests specific functions for different forms.

Distributions of phenolic compounds, yellow pigments and oxidative enzymes in wheat grains and their relation to antioxidant capacity of bran and debranned flour

“…The POX activity was found to be abundant in bran. Its presence was also reported in the aleurone layer, scutellum and endosperm (Fraignier et al, 2000). According to our study, the average value of durum wheat bran for the POX activity was about 3.7-fold higher than that of debranned durum wheat flour.…”

“…However, no significant difference in the mean POX activity was observed between debranned flour and bran of bread wheat (Table 4). Fraignier et al (2000) demonstrated the presence of multiple isoforms of POX in the durum wheat grain, also with a tissue-specificity, suggesting for each of them a particular function. The bran POX, in the presence of hydrogen peroxide, may act to strengthen cell walls through lignin cross-linking, thus inhibiting fungal penetration and providing the protection of embryo and nutrient-rich endosperm (Jerkovi c et al, 2010).…”

The colours of durum wheat: a review

“…Carotenoid pigment degradation is also affected by the peroxidases (PERs), a class of enzymes that can oxidise a large number of compounds at the expense of hydrogen peroxide (Fraignier et al 2000). Fortunately, PERs do not show activity during pasta processing, probably because of the lack of availability of hydrogen peroxide (Icard-Vernière and Feillet1999;Feillet et al 2000).…”

Environment during grain filling affects pasta color

“…Matsuo and Irvine (1967) reported that the inherited brownness was the result of nonenzymatic soluble proteins. Contrarily, Fraignier, Michaux‐Ferrière, and Kobrehel (2000) suggested that enzymatic brownness based on a POD isoform P‐5 was found in greater amount in the endosperm of a cultivar of durum wheat with darker pasta could be responsible for genotypic differences in brownness of pasta. On the other hand, PPO activity levels in wheat have been more associated with the growing environment than genotype (Kiszonas, Fuerst, & Morris, 2013; Park et al., 1997).…”