Transgenic Sorghum with Altered Kafirin Synthesis: Kafirin Solubility, Polymerization, and Protein Digestion

• Published in: Journal of agricultural and food chemistry Vol. 59; no. 17; pp. 9265 - 9270
• Main Authors: da Silva, Laura S, Taylor, Janet, Taylor, John R. N
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 14-09-2011
• Subjects: alcohols; Amylases - metabolism; Biological and medical sciences; Cereal and baking product industries; Chemical Aspects of Biotechnology/Molecular Biology; digestibility; digestible protein; Digestion; Disulfides - chemistry; Food industries; Fundamental and applied biological sciences. Psychology; mutants; Pepsin A - metabolism; Plant Proteins - biosynthesis; Plant Proteins - chemistry; Plant Proteins - isolation & purification; Plant Proteins - metabolism; Plants, Genetically Modified - metabolism; Polymerization; protein bodies; proteins; Solubility; Sorghum - metabolism; starch; Starch - metabolism; kafirin; polymerization; Sorghum; protein digestibility; transgenic; disulfide cross-linking; Monocotyledones; Solubility; Polymerization; Digestion; Protein; Synthesis; Gramineae; Angiospermae; Cereal; Spermatophyta; Sorghum (food); Genetically modified organism; Digestibility
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf201878p

Transgenic sorghum (TG) lines with altered kafirin synthesis, particularly suppression of γ-kafirin synthesis, and improved protein quality have been developed. The proportion of kafirin extracted with 60% tert-butyl alcohol alone was greatly increased in the TG lines. However, the total amount of kafirin remained unchanged. Further, in the TG lines, the kafirin was much less polymerized by disulfide bonding. There was also evidence of compensatory synthesis of other kafirin proteins. Cooked protein digestibility was increased in the TG form, even after removal of interfering starch. The TG protein bodies were intermediate in appearance between the normal type and the invaginated high digestibility mutants. Hence, the increased protein digestibility of these TG lines is probably related to their lower levels of disulfide-bonded kafirin polymerization, allowing better access of proteases. This work appears to confirm that disulfide bond formation in kafirin is responsible for the reduced protein digestibility of cooked sorghum.