Overphosphorylation of milk caseins by a recombinant protein kinase CK2 catalytic subunit.
Milk caseins have been phosphorylated by a recombinant protein kinase CK2 catalytic subunit from Schizosaccharomyces pombe (rspCK2alpha). Phosphate incorporation stoechiometries into purified caseins and into native phosphocaseinate, a substrate exhibiting a micellar-like structure, were determined. We incorporated 2.01 mol of P/mol of alpha-casein, 6.46 mol of P/mol of beta-casein, up to 0. 29 mol of P/mol of kappa-casein in 4 h, and more than 1.36 mol of P/mol of casein into phosphocaseinate under optimized conditions. Phosphocaseinate was sequentially phosphorylated; beta-caseins being labeled at first; alpha-caseins being labeled later; and to a lower extend, kappa-caseins were the last to be phosphorylated. The solubility of phosphocaseinate micelles increased by 1.34 from 65 to 87%, and its rennetting time was increased 2.88 times. These results are discussed in terms of plausible structural organization of caseins micelles and the effect of phosphorylation on their structure.
Pitois
E
E
Laboratoire de Chimie Biologique, INRA INA-PG, Centre de Biotechnologie Agro-Industrielle, 78850 Thiverval-Grignon, France.
Chardot
T
T
Meunier
J C
JC
D000818:Animals; D002364:Caseins / Q000378:metabolism*; D002611:Cheese; D006801:Humans; D008823:Micelles; D008892:Milk; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism
D002364:Caseins; D008823:Micelles; D011994:Recombinant Proteins; D011494:Protein Kinases