P4-ATPase flippase which catalyzes the hydrolysis of ATP coupled to the transport of aminophospholipids from the outer to the inner leaflet of various membranes and ensures the maintenance of asymmetric distribution of phospholipids. Phospholipid translocation seems also to be implicated in vesicle formation and in uptake of lipid signaling molecules. May play a role in phospholid transport across membranes and in acrosome formation. ATP + H2O + phospholipidSide 1 = ADP + phosphate + phospholipidSide 2. Highly expressed in testis. Not detected in testis until 18 days postpartum. At 22 days postpartum, levels increase and remain constant during adulthood. During spermatogenesis, expressed from pachytene spermatocytes to mature sperm. Belongs to the cation transport ATPase (P-type) (TC 3.A.3) family. Type IV subfamily.