Protein Kinase Classification
About 2% of all eukaryotic genes are protein kinases, with over 500 kinases in mammalian genomes. To organize this diversity and compare genes between distant organisms, we developed a classification scheme for protein kinases. Kinases are divided into 9 main groups, and each group is then split into families, and often subfamilies. This classification was first used in our human kinome paper in 2002, and is largely based on an earlier one by Hunter and Hanks with substantial changes and additions. It is under continuous development and expansion as new kinomes are explored.