Cyclin-dependent kinase 5 (Cdk5) is a serine/threonine kinase that is predominantly active in neuronal tissues. With p25 or p35, Cdk5 phosphorylates a range of proteins, including histone H1 and tau. Cdk5 substrate is a synthetic peptide (PKTPKKAKKL) corresponding to a sequence of histone H1. It is phosphorylated by Cdk5 with a Km value of 5 μM.
