label: (6S)-5,6,7,8-tetrahydrofolate + L-serine => (6R)-5,10-methylene-5,6,7,8-tetrahydrofolate + glycine + H2O
label_lc: (6s)-5,6,7,8-tetrahydrofolate + l-serine => (6r)-5,10-methylene-5,6,7,8-tetrahydrofolate + glycine + h2o