A class I phosphatidylinositol 3-kinase complex that possesses 1-phosphatidylinositol-4-phosphate 3-kinase activity; comprises a catalytic class IB phosphoinositide 3-kinase (PI3K) subunit and an associated regulatory subunit that is larger than, and unrelated to, the p85 proteins present in class IA complexes. Class IB PI3Ks are stimulated by G-proteins and do not interact with the SH2-domain containing adaptors that bind to Class IA PI3Ks.
class IB PI3K complex