sentence: In addition to substrates annotated in iPTMnet and KEA databases , we searched for candidate CK2 substrates among downregulated phosphopeptides based on : ( 1 ) the presence of CK2 consensus sequence , ( 2 ) the enzyme – substrate predictions retrieved from NetworKIN database , ( 3 ) the dataset of high confidence CK2 substrates reported by Bian et al. [ 55 ] , and ( 4 ) the phosphoproteins that interact with protein kinase CK2 according to the Metascape database ( Table S6 ) .