Crosstide is a synthetic peptide derived from glycogen synthase kinase-3 beta (GSK-3). Crosstide functions as substrate for Akt/PKB (protein kinase B) and is also recognized by MAPKAP kinase-1 and p70S6K, Crosstide also displays similar selectivity towards PKB alpha, PKB beta and PKB gamma isoforms. The fluorescent and biotinylated versions of crosstide demonstrate similar enzymic activity.
