Casein kinase I isoform alpha (EC 2.7.11.1) (CKI-alpha) (CK1); Casein kinases are operationally defined by their preferential utilization of acidic proteins such as caseins as substrates. It can phosphorylate a large number of proteins. Participates in Wnt signaling. Phosphorylates CTNNB1 on 'Ser-45' (364 aa)