preferred_name: L-threonine + L-serine => L-seryl-L-threonine + H2O
preferred_name_lc: l-threonine + l-serine => l-seryl-l-threonine + h2o
label: L-threonine + L-serine => L-seryl-L-threonine + H2O
label_lc: l-threonine + l-serine => l-seryl-l-threonine + h2o