The Use of Ascorbic Acid to Promote the Polymerization of 11S Globulin

Abstract

We investigated the effects of L-ascorbic acid (AsA) on 11S globulin, which was reduced by 2-mercaptoethanol. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis verifi ed that AsA promoted the polymerization of 11S globulin via the formation of disulfi de bridges. The generation of thiyl radicals (S·) in 11S globulin was examined by electron spin resonance spectroscopy coupled with spin trapping. The superoxide anion radical (O 2 -) was produced by the photoactivation of ribofl avin. A typical line shape was observed for S·. Staining with nitroblue tetrazolium dye confi rmed that O 2 -was produced in the 11S globulin solution due to the autooxidation of AsA. Although the 11S globulin lacking AsA did not yield a rigid gel, the sample containing AsA successfully yielded a rigid gel. Thus, it is clear that O 2 -generated during AsA oxidation exerts benefi cial effects on 11S globulin in its reduced form.Keywords: vitamin C, polymerization, 11S globulin, superoxide anion radical, electron spin resonance (ESR), thiyl radical, disulfi de (SS) bridges *To whom correspondence should be addressed. Email: knishimu@dwc.doshisha.ac.jp IntroductionIn several studies (Sarwin et al., 1993; Hahn and Gosch, 1998; Grosch and Wiesre, 1999;Koehler, 2003), which we have described in previous papers Nishimura, 2006a, 2006b), the benefi cial effects that L-ascorbic acid (AsA) exerts on bread have been represented by the scheme shown in Fig. 1 -A (Kuninori and Nishiyama, 1993). The mechanism by which AsA improves the quality of heat-induced fi sh gel (kamaboko) is considered to be as represented in Fig. 1-A, since the addition of dehydro-L-ascorbic acid (DHA) to raw fish paste (surimi) increases the strength of heat-induced fi sh gel (kamaboko) (Yoshinaka et al., 1972). However, based on the results obtained in a series of previous studies (Nishimura et al., 1992a(Nishimura et al., , 1992b(Nishimura et al., , 1994(Nishimura et al., , 1996Miyamoto and Nishimura, 2006a), Nishimura et al. clarifi ed that the beneficial effects exerted by AsA on heat-induced fi sh gel (kamaboko) were due to a different mechanism involving the superoxide anion radical (O 2 -), shown in Fig. 1 -B (Nishimura et al., 1996;Miyamoto and Nishimura, 2006a) and that AsA acted more readily on the subfragment-1 region of myosin (Ikeuchi et al., 2007). Furthermore, Miyamoto and Nishimura (2006b) observed that O 2 -promotes polymerization among peptides derived from wheat proteins via the formation of disulfi de (SS) bridges, in keeping with the mechanism shown in Fig. 1-B. This suggests that AsA may exert beneficial effects for not only on myosin but also on other food proteins in the manner indicated in Fig. 1-B. Soy protein, the most popular plant protein source to serve as an ingredient in the food industry, is not a homogeneous protein. The major protein fractions in soybean are 2S, 7S, 11S, and 15S globulins, of which 7S and 11S globulins are able to form intermolecular SS bonds, leading to protein insolubility and increased turbidity and visc...

Occurrence of Thiyl Radical on a Myosin derived from Carp by Superoxide Anion Radical

“…However, it is clarified from the results presented here that the beneficial effect of AsA was due to the mechanism proposed by Nishimura and colleagues (1996;2006a), which involves O 2 -generated during the oxidation of AsA. We have already found the generation of S· and the polymer-formation of 11S globulin by O 2 - (Nishimura et al, 2008), suggesting the possibility that the beneficial effect of AsA is brought about according to the same mechanism in other proteins. In contrast to heat-induced fish gel, yeast rapidly con- The mixture for myosin used in Fig.…”