The transhydrogenation between NADH and NADP is coupled to respiration and ATP hydrolysis and functions as a proton pump across the membrane. H(+)(in) + NAD(+) + NADPH = H(+)(out) + NADH + NADP(+) Heterodimer of an alpha (PntA) and a beta (PntB) chain. Belongs to the AlaDH/PNT family.