Thrombin inhibitor activated by the glycosaminoglycans, heparin or dermatan sulfate. In the presence of the latter, HC-II becomes the predominant thrombin inhibitor in place of antithrombin III (AT-III). Also inhibits chymotrypsin, but in a glycosaminoglycan-independent manner. Peptides at the N-terminal of HC-II have chemotactic activity for both monocytes and neutrophils. Expressed predominantly in liver. Also present in plasma. The N-terminal acidic repeat region mediates, in part, the glycosaminoglycan-accelerated thrombin inhibition. Phosphorylated by FAM20C in the extracellular medium. The disease is caused by variants affecting the gene represented in this entry. Belongs to the serpin family. Extended N-terminus.