passages.id: split_5_test_2633_passage
passages.type: progene_text
passages.text: At neutral pH , the ATPase activity of the SERCA3 enzymes was not significantly enhanced upon permeabilization of the microsomal vesicles with calcium ionophore , indicating a difference from SERCA1a with respect to regulation of the lumenal Ca(2+) level ( either an enhanced efflux of lumenal Ca(2+) through the pump in E(2) form or insensitivity to inhibition by lumenal Ca(2+) ) .