phosphorylation and characterisation of soybean isolate and its beta-conglycinin component by casein kinase II

• Published in: Journal of the science of food and agriculture 1999-07, Vol.79 (9), p.1179-1182
• Main Authors: Burghoffer, C, Chardot, T, Meunier, J.C
• Format: Article
• Language: English
• Subjects: Animal, plant, fungal and microbial proteins, edible seaweeds and food yeasts; Bioconversions. Hemisynthesis; Biological and medical sciences; Biotechnology; calcium chloride; casein kinase II; Food industries; functional properties; Fundamental and applied biological sciences. Psychology; glycinin; iron binding capacity; Methods. Procedures. Technologies; phosphorylation; protein isolates; Research and development. New food products, dietetic foods and beverages; Saccharomycetales; solubility; soybean; soybeans; Yarrowia lipolytica; β-conglycinin
• ISSN: 0022-5142; 1097-0010
• DOI: 10.1002/(SICI)1097-0010(19990701)79:9<1179::AID-JSFA345>3.0.CO;2-Q

A commercial soybean isolate was phosphorylated using casein kinase II purified from the yeast Yarrowia lipolytica. Both major reserve proteins, beta-conglycinin and glycinin, were phosphorylated in a sequential way. The soybean isolate incorporated up to 0.7 mol phosphate per mole in 2 h. It was found that the phosphoester bonds were stable over time. The solubility of the phosphorylated isolate with respect to pH was not dramatically increased in comparison with the native one. However, counting the radioactivity of 32P incorporated into the proteins (only the solubility of the phosphorylated proteins was measured in this case) showed that the solubility of the proteins was dramatically improved (up to 90% solubility for phosphorylated beta-conglycinin at pH 4). beta-Conglycinin became more soluble in the presence of CaCl2 upon phosphorylation; this was not the case for the isolate. The iron-binding capacity of the soy isolate and beta-conglycinin was significantly improved after phosphorylation (two and six times respectively).