GO:0035004

Catalysis of the reaction: ATP + a phosphatidylinositol = ADP + a phosphatidylinositol 3-phosphate. This reaction is the addition of a phosphate group to phosphatidylinositol or one of its phosphorylated derivatives at the 3' position of the inositol ring. [GOC:bf, PMID:10209156, PMID:9255069]