Non‐enzymatic protein modification by the Maillard reaction reduces the activities of scavenging enzymes in Vigna radiata

Abstract

The non-enzymatic modification of proteins through the Maillard reaction plays an important role in the loss of seed viability during seed storage. In the present study we examined whether the Maillard reaction reduces the activities of scavenging enzymes in Vigna radiata (mung bean) seeds during storage. Seeds were stored under various conditions for different duration. Maillard products were monitored by measuring protein fluorescence, and the activities of glutathione reductase (GR), superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and peroxidase (POX) were determined. The accumulation of Maillard products in seed axes increased during storage with increasing moisture content and temperature, and was correlated with the decline in seed vigour. The activities of GR, CAT and APX decreased in proportion to the increase in Maillard products at all the moisture contents and temperatures tested. These enzymatic changes were also correlated with seed vigour. However, the activities of SOD and POX remained unchanged and appeared to be less sensitive to the Maillard reaction.

Protein deterioration and longevity of quinoa seeds during long-term storage

“…Spectra differed according to the protein fractions and were coincident at different storage conditions (data not shown). The fluorescence peak attributed to the presence of AGE in seed protein fractions is observed when excited between 320 and 380 nm (Murthy & Sun, 2000;Murthy et al, 2002Murthy et al, , 2003, which is significantly different to the intrinsic protein fluorescence emitted by tryptophan (excitation at 280 nm/emission at 390 nm), and the basic residues of arginine and lysine are generally involved in the formation of Maillard-related fluorescent compounds (Tessier, Monnier, & Kornfield, 2002).…”

“…These modifications can take place by non-enzymatic glycosylation with reducing sugar or by reaction with aldehydes produced from free radical-mediated lipid peroxidation (Murthy & Sun, 2000;Priestley, 1986;Priestley & Leopold, 1983;Sun & Leopold, 1995;Wettlaufer & Leopold, 1991). The Maillard reaction may contribute to seed ageing through the chemical alteration of functional proteins, thus depressing metabolic capability, and reducing the ability of the metabolic system to limit free radical damage and to repair the damage during germination (Murthy, Liang, Kumar, & Sun, 2002).…”

“…Protein fluorescence analysis has regularly been used to study protein modification by this reaction during seed storage. Several authors have previously reported the development of a fluorescence peak attributed to the presence of advanced glycosilation end-products (AGEs) in aqueous solutions of seed proteins, yet fluorescence spectra of various AGE products slightly differ between species, i.e., excitation/emission wavelengths of 375/ 440 nm for soybean (Sun & Leopold, 1995), 370/440 nm for onion, tomato and cauliflower (Baker & Bradford, 1994), 350/420 nm for mungbean (Murthy, Kumar, & Sun, 2003;Murthy & Sun, 2000;Murthy et al, 2002). Nevertheless, Baker and Bradford (1994) did not find correlation between fluorescence development and seed deterioration in onion, cauliflower, tomato, carrot, broccoli and lettuce, probably because of interference from other fluorescent compounds, such as polyphenols, present in seed coats.…”

Changes in germinability, lipid peroxidation, and antioxidant enzyme activities in pear stock (Pyrus betulaefolia Bge.) seeds during room- and low-temperature storage

“…This mechanism removes superoxide and thus decreases the risk of hydroxyl radical formation from superoxide via the metal-catalyzed Haber-Weiss-type reaction (Gutteridge and Halliwell 1990). Previous data obtained from various species, including soybean (Murthy et al 2002), cotton (Goel et al 2003), beech (Pukacka and Ratajczak 2005), and sunflower (Bailly et al 1996;Kibinza et al 2006), have demonstrated that loss of seed viability is associated with a decrease in SOD. The results showed that loss of pear stock seed viability at room is also associated with a decrease in SOD.…”

Seed Vigor Variation of <i>Agave durangensis</i> Gentry (Agavaceae)

“…Some authors have suggested the use of that potential as vigor indicator [44]; according to those authors the seeds of La Parrilla, with the highest antioxidant potential (50.35%, Table 6) would display the uppermost vigor. The antioxidant potential, before and during germination, is determined by the antioxidant enzymatic activity of the embryo cells once these are hydrated [44][45][46], and by the non-enzymatic antioxidant compounds found in an active way in seeds, independently of the hydratation of seeds [47,48]. Phenolics are among those compounds; actually they are the main responsible in maintaining the growth potential of the embryo at storage conditions (pregerminatory stage) until the imbibition allows the activation of the antioxidant mechanism directed by enzymes [3].…”