Protein kinase B (PKB), also known as Akt (PKB/Akt), is a serine/threonine phosphoryl transferase and a downstream effector of the phosphoinositol–3 kinase (PI3K) signaling.
The AKT protein kinase (also referred to as protein kinase B or Rac-protein kinase) was initially identified as an acute transforming component of the AKT8 virus isolated from a murine T cell lymphoma1, 2.
PKB/Akt belongs to the AGC subfamily of the protein kinase superfamily, which consists of 518 members in humans and is conserved from primitive metazoans to humans3. 
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