Characterization of peptides generated in proteolytic digest of steamed rice grains by sake koji enzymes

• Published in: Journal of bioscience and bioengineering 2007-10, Vol.104 (4), p.251-256
• Main Authors: Hashizume, Katsumi, Okuda, Masaki, Numata, Mineyo, Zhou, Yan, Koseki, Takuya
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Biological and medical sciences; Biotechnology; Fundamental and applied biological sciences. Psychology; glutelin; Molecular Sequence Data; Oryza - chemistry; Oryza sativa; Peptide Hydrolases - chemistry; peptide mass fingerprinting; peptides; Peptides - chemistry; Peptides - metabolism; sake; Seeds - chemistry; Steam; Wine
• ISSN: 1389-1723; 1347-4421
• DOI: 10.1263/jbb.104.251

High-molecular-weight peptides (approximately 10–30 kDa) generated in a digest of steamed rice grains by sake koji enzymes were characterized. Among 13 major spots resolved by 2-D gel electrophoresis, 12 contained peptides having N-termini of rice glutelin as determined by mass fingerprinting analysis and/or MS/MS. The source of these peptides was presumed to be the acidic subunit of rice glutelin. An addition of up to 25% glucose in the digestion of an isolated rice protein body induced the accumulation of these peptides. The level of accumulation of these peptides in the digest of 70% polished rice samples correlated well with the crude protein content of the rice grains. The degree of accumulation of these peptides in Yamadanishiki and low-polish-rate rice was low, whereas that observed in 90% polished rice samples was extremely low.