Class I PI 3-kinases

Class I PI 3-kinases are a subgroup of the enzyme family, phosphoinositide 3-kinase that possess a common protein domain structure, substrate specificity, and method of activation. Class I PI 3-kinases are further divided into two subclasses, class IA PI 3-kinases and class IB PI 3-kinases.

Class IA PI 3-kinases
Class IA PI 3-kinases are activated by receptor tyrosine kinases (RTKs).

There are three catalytic subunits that are classified as class IA PI 3-kinases:
 * p110α
 * p110β
 * p110δ

There are currently five regulatory subunits that are known to associate with class IA PI 3-kinases catalytic subunits:


 * p85α and p85β
 * p55α and p55γ
 * p50α

Class IB PI 3-kinases
Class IB PI 3-kinases are activated by G-protein-coupled receptors (GPCRs).

The only known class IB PI 3-kinase catalytic subunit is p110γ.

There are two known regulatory subunits for p110γ:
 * p101
 * p84/ p87PIKAP.