preferred_name: L-tryptophan(out) + H(+)(out) => L-tryptophan(in) + H(+)(in)
preferred_name_lc: l-tryptophan(out) + h(+)(out) => l-tryptophan(in) + h(+)(in)
label: L-tryptophan(out) + H(+)(out) => L-tryptophan(in) + H(+)(in)
label_lc: l-tryptophan(out) + h(+)(out) => l-tryptophan(in) + h(+)(in)