preferred_name: nitrite(in) + H(+)(out) <=> nitrite(out) + H(+)(in)
preferred_name_lc: nitrite(in) + h(+)(out) <=> nitrite(out) + h(+)(in)
label: nitrite(in) + H(+)(out) <=> nitrite(out) + H(+)(in)
label_lc: nitrite(in) + h(+)(out) <=> nitrite(out) + h(+)(in)