Has glycerophosphoinositol inositolphosphodiesterase activity and specifically hydrolyzes glycerophosphoinositol, with no activity for other substrates such as glycerophosphoinositol 4-phosphate, glycerophosphocholine, glycerophosphoethanolamine, and glycerophosphoserine. Accelerates the program of osteoblast differentiation and growth. May play a role in remodeling of the actin cytoskeleton (By similarity).