Heparin inhibits Xa by
Heparin contains pentasaccharide unit that activates Antithrombin III & inhibits factor Xa (Thus it is a indirect thrombin inhibitor).
Unfractionised heparin also contains a heteropolysaccharide unit that inhibits factor II a.
LMWH lacks this heteropolysacchoride unit and therefore inhibitors factor Xa only.
Blocking vitamin K mediated activation of Xa
Activating Antithrombin III
Direct breakdown of Xa
Blocking P2 Y12 receptor of ADP