This family includes heparin lyase I, EC:184.108.40.206. Heparin lyase I depolymerizes heparin by cleaving the glycosidic linkage next to an iduronic acid moiety. The structure of heparin lyase I consists of a beta-jelly roll domain with a long, deep substrate-binding groove and an unusual thumb domain containing many basic residues extending from the main body of the enzyme. This family also includes glucuronan lyase, EC:220.127.116.11. The structure glucuronan lyase is a beta-jelly roll.