Characterization of endogenous enzymes of milled rice and its application to rice cooking

Mabashi

et al. 2010

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The distribution of starch-degrading enzymes in dormant rice grains was investigated with specific antibodies against α-glucosidases, α-amylases, and β-amylases. The α-glucosidases were predominantly localized in the inner endosperm. The α-amylases were mainly localized in the outer layers, and the β-amylases were distributed in whole grains. We propose a model to demonstrate how these enzymes degrade starch during rice cooking.

Section: Discussionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 97%

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Different Distributions of .ALPHA.-Glucosidases and Amylases in Milling Fractions of Rice Grains

Mabashi

et al. 2010

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Section: Introductionmentioning

confidence: 99%

Distribution of Starch-degrading Enzymes in Rice Grains of Different Cultivars and Elution Behavior during Cooking

Kasai

2013

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Rice grains contain starch-degrading enzymes, including α-glucosidases, α-amylases, β-amylase, pullulanase and isoamylases. We investigated the distribution of these enzymes in raw rice grains, and their elution behavior during cooking in Nipponbare and Habutaemochi cultivars. Different distributions and elution behaviors were observed among the different cultivars. These results suggest that differences among cultivars with regard to activation and starch degradation by these enzymes during rice cooking should be taken into consideration.Keywords: starch-degrading enzymes, immunoblot, rice cooking, elution Abbreviations: PBSD medium, sodium phosphate buffer (pH 7.0) containing DTT and NaCl; SDS-PAGE, sodium dodecyl sulfate polyacrylamide gel electrophoresis *To whom correspondence should be addressed. E-mail: ookura@affrc.go.jp IntroductionRice (Oryza sativa) is a major food in Asian countries, including Japan. Extensive studies have been carried out to determine how preferable taste can be achieved in rice cooking. It was found that physical properties, such as stickiness and hardness (Okabe, 1979;Maruyama, 1991;Kainuma, 1992;Okadome et al., 1996;Okadome et al., 1999), and chemical components, such as sugars and amino acids, contribute to the taste of cooked rice (Matsuzaki et al., 1992;Tajima et al., 1992;Ikeda, 2001). The amounts of sugars (reducing sugars and oligosaccharides) and amino acids are correlated with the activities of starch-degrading enzymes and proteases, which are activated during cooking (Maruyama et al., 1981;Kasai et al., 2000;Maruyama, 2002). Kasai et al. measured the amounts of reducing sugars and free sugars, which remained in the rice grains or eluted into the cooking water at the point of soaking, heating and murashi duration. They revealed that reducing sugars and glucose showed the largest increase in a temperature range of 40 − 60℃ during cooking in both rice grains and cooking water. They reported this was due to the activation of enzymes to convert starch to reducing sugars in this temperature range. Mabashi et al. (2010) analyzed the hydrolytic activities of the endogenous starch-degrading enzymes for the soluble starch in the various cultivars, and revealed that 60℃ was the common key temperature in various cultivars for the production of glucose by endogenous enzymes.The enzyme isoforms that exist in dormant rice and degrade starch granules during germination are α-amylases (EC 3.2.1.1) (Mitsui et al., 1996;Yu et al., 1996), β-amylases (EC 3.2.1.2) (Matsui et al., 1975;Yamaguchi et al., 1999), isoamylase (EC 3.2.1.68) , pullulanase (EC 3.2.1.41) (Takeuchi et al., 1999) and α-glucosidases (EC 3.2.1.20) (Takahashi et al., 1971;Matsui et al., 1988). Two studies have demonstrated that rice grains contain more than 10 α-amylase isoforms (Daussant et al., 1983;Mitsui et al., 1996). These isoforms are classified into two groups based on their optimal temperatures: α-amylase I (70℃) and α-amylase II (37℃) (Mitsui et al., 1996). These α-amylase isoforms are strongly induced during germ...

“…Fractions containing a 100 kDa band were collected and used for antibody production as described above. The 100 kDa band sequence was confirmed by MALDI-TOF/TOF analyzer (ABI 4800 Plus, CA, USA) as previously described (Mabashi et al, 2009).Immunoblot For immunoblots, the electrophoresed gels were equilibrated with a blotting buffer (50 mM Tris, 5 mM glycine, 0.037% SDS). The proteins were then transferred to nitrocellulose membranes (Bio-Rad) with a transblotting system (NIHON EIDO, Tokyo, Japan) (Towbin et al, 1979).…”

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confidence: 99%

Elution Behavior Analysis of Starch Degrading Enzymes During Rice Cooking with Specific Antibodies

Tsukui

et al. 2012

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Rice grains contain starch degrading enzymes, including α-glucosidases, α-amylases, β-amylases, pullulanase and isoamylases. To investigate the elution behavior of these enzymes from rice grains into cooking water during rice cooking, we separated cooking water from rice grains after soaking (20℃) and when the temperature reached 40℃ and 60℃ during cooking. Immunological detection of these enzymes in rice grains and cooking water was carried out with SDS-PAGE and immunoblot. Bands corresponding to pullulanase, α-glucosidase, isoamylase 1, and α-amylase E were detected in both rice grains and cooking water at each temperature. Bands corresponding to α-amylases A + B and H were not detected in rice grains, but were detected in the cooking water at each temperature. The β-amylase band was detected in rice grains but was not detected in cooking water. These results suggest that the amount of enzyme eluted into cooking water depends on enzyme localization and quantity in rice grains.Keywords: rice, starch degrading enzymes, immunoblot, rice cooking, elution Abbreviations: PBSD medium, sodium phosphate buffer (pH 7.0) containing DTT and NaCl; SDS-PAGE, sodium dodecyl sulfate polyacrylamide gel electrophoresis *To whom correspondence should be addressed. E-mail: ookura@affrc.go.jp IntroductionRice (Oryza sativa) is a major food in Asian countries, including Japan. Extensive studies have been carried out to determine how a preferable taste can be achieved in rice cooking. It was found that physical properties such as stickiness and hardness (Maruyama, 1991;Kainuma, 1992), and chemical components such as sugars and amino acids contribute to the taste of cooked rice (Matsuzaki et al., 1992;Tajima et al., 1992;Ikeda, 2001). The amounts of sugars (reducing sugars and oligosaccharides) and amino acids correlate with the activities of starch-degrading enzymes and proteases, which are activated during cooking (Maruyama et al., 1981;Kasai et al., 2000;Maruyama, 2002).The enzyme isoforms present in dormant rice, which degrade starch granules during germination, include: α-amylases (EC 3.2.1.1) (Mitsui et al., 1996;Yu et al., 1996), β-amylases (EC 3.2.1.2) (Matsui et al., 1975;Yamaguchi et al., 1999), isoamylases (EC 3.2.1.68) (Fujita et al., 1999), pullulanase (EC 3.2.1.41) (Takeuchi et al., 1999), and α-glucosidases (EC 3.2.1.20) (Takahashi et al., 1971;Matsui et al., 1988). Two studies demonstrated that rice grains contain more than 10 types of α-amylase isoforms (Daussant et al., 1983;Mitsui et al., 1996). These isoforms are classified into two groups on the basis of their optimum temperature: α-amylase I (70℃) and α-amylase II (37℃) (Mitsui et al., 1996). These α-amylase isoforms are remarkably induced during germination (Alpi and Beevers, 1983; Perata et chi (Hokkaido University, Japan). The polyclonal antibody against isoamylase 1 was kindly provided by Dr. Nakamura (Akita Prefectural University, Japan).Rice Sample Brown rice (Oryza sativa L., cv. Koshihikari) was purchased from Uonuma in Niigata in 2008 and stored at 4℃ u...