2 phosphate + 2 H(+)(out) => diphosphate + H2O + H(+)(in)
2 phosphate + 2 h(+)(out) => diphosphate + h2o + h(+)(in)
2 phosphate + 2 H(+)(out) => diphosphate + H2O + H(+)(in)
2 phosphate + 2 h(+)(out) => diphosphate + h2o + h(+)(in)