Catalytic subunit of the V1 complex of vacuolar(H+)-ATPase (V-ATPase), a multisubunit enzyme composed of a peripheral complex (V1) that hydrolyzes ATP and a membrane integral complex (V0) that translocates protons (By similarity). V-ATPase is responsible for acidifying and maintaining the pH of intracellular compartments (By similarity). VDE is an endonuclease that can cleave at a site present in a VMA1 allele that lacks the derived endonuclease segment of the open reading frame; cleavage at this site only occurs during meiosis and initiates 'homing', a genetic event that converts a VMA1 allele lacking VDE into one that contains it. ATP + 4 H(+)(in) + H2O = ADP + 5 H(+)(out) + phosphate V-ATPase is a heteromultimeric enzyme composed of a peripheral catalytic V1 complex (components A to H) attached to an integral membrane V0 proton pore complex (components: a, c, c', c'', d, e, f and VOA1). Membranes of various intracellular acidic compartments. This protein undergoes a protein self splicing that involves a post-translational excision of the VDE intervening region (intein) followed by peptide ligation. Belongs to the ATPase alpha/beta chains family.