an S-substituted L-cysteine + glycine => an S-substituted L-cysteinylglycine + H2O
an s-substituted l-cysteine + glycine => an s-substituted l-cysteinylglycine + h2o
an S-substituted L-cysteine + glycine => an S-substituted L-cysteinylglycine + H2O
an s-substituted l-cysteine + glycine => an s-substituted l-cysteinylglycine + h2o