Definition of the acceptor substrate binding specificity in plant xyloglucan endotransglycosylases using computational chemistry

The visualisation of the MD trajectory of the XG-OS7 donor and Xyl-OS4 acceptor substrates in the active site of PttXET16A reveals the instability of the acceptor. After 20 ns the Xyl-OS4 chain changes its position and approaches the loop with S257. However, unlike Cello-OS4 this interaction does not stabilise the acceptor. After 50 ns the first signs of destabilisation of Xyl-OS4 can be observed, and after 460 ns its chain moves into a position that is unfavourable for glycosidic bond formation. Conversely, the Xyl-OS4 acceptor in the active site of TmXET6.3 remains stable during the duration of the MD simulation.