preferred_name: serotonin(out) + 2 H(+)(in) => serotonin(in) + 2 H(+)(out)
preferred_name_lc: serotonin(out) + 2 h(+)(in) => serotonin(in) + 2 h(+)(out)
label: serotonin(out) + 2 H(+)(in) => serotonin(in) + 2 H(+)(out)
label_lc: serotonin(out) + 2 h(+)(in) => serotonin(in) + 2 h(+)(out)