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.
See also Phosphoinositide 3-kinase#Class I Phosphoinositide 3-kinase inhibitor
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