a tissue-specific casein kinase , purified from the golgi-enriched-membrane fraction of guinea-pig lactating mammary gland ( gef-ck ) , readily phosphorylates the synthetic peptide ser-glu5 , a good substrate of casein kinase-2 , and several derivatives varying for the number and position of acidic residues on the c-terminal side of serine , except those lacking an acidic side chain at position +2 .
C0054846
casein kinase
C0108555
casein kinase-2