Mitogen-activated protein kinase kinase
（重定向自MAPKK）
Mitogen-activated protein kinase kinase (also known as MAP2K, MEK, MAPKK) is a kinase enzyme which phosphorylates mitogen-activated protein kinase (MAPK).
MAP2K is classified as EC2.7.12.2.
There are seven genes:
The activators of p38 (MKK3 and MKK6), JNK (MKK4 and MKK7), and ERK (MEK1 and MEK2) define independent MAP kinase signal transduction pathways. The acronym MEK derives from MAPK/ERK Kinase.