Dear Enrico, you can find information on PDB entries with carbohydrates in the GLYCOSCIENCES.de database: http://www.glycosciences.de/database/index.php
To find entries with O-Glycans linked to Thr you can use the substructure search at http://www.glycosciences.de/database/start.php?action=form_structure_matrix (please make sure that you tick the checkbox "with PDB entries" to limit the search to carbohydrates that are found in the PDB). Just type THR into the center field of one of the upper input area. This will reveal all glycan chains in the database that feature a Thr residue and are represented in PDB structures. There might be more entries in the PDB than in our database, because we try and skip erroneous structures, e.g. those with a mismatch between PDB residue name and residue present in the coordinates (unless it is obvious that the coordinates are correct and just the residue name is wrong, but for O-glycans that's often difficult to tell). Best regards, Thomas