by subjecting beta a-casein and its nh2-terminal peptide to the combined action of almond acid phosphatease and purified yeast protein kinase , it was determined that the phosphorylation and dephosphorylation reactions proceed randomly , i.e. , all seryl phosphate residues are equally susceptible and that the rate of phosphorylation decreases drastically as the number of bound phosphate groups in the substrate diminishes .
C0031727
kinase
C0031715
phosphorylation