preferred_name: L-leucine(out) + L-methionine(in) => L-leucine(in) + L-methionine(out)
preferred_name_lc: l-leucine(out) + l-methionine(in) => l-leucine(in) + l-methionine(out)
label: L-leucine(out) + L-methionine(in) => L-leucine(in) + L-methionine(out)
label_lc: l-leucine(out) + l-methionine(in) => l-leucine(in) + l-methionine(out)