Seven pharmaceutical heparins were investigated by oligosaccharide mapping by digestion with heparin lyase 1, 2 or 3, followed by high performance liquid chromatography analysis. The structure of one of the prepared mapping standards, ΔUA-Gal-Gal-Xyl-O-CH 2 CONHCH 2 COOH, (where ΔUA is 4-deoxy-α-L-threo-hex-4-eno-pyranosyluronic acid, Gal is β-D-galactpyranose, and Xyl is β-D-xylopyranose) released from the linkage region using either heparin lyase 2 or heparin lyase 3 digestion, is reported for the first time. A size-dependent susceptibility of site cleaved by heparin lyase 3 was also observed. Heparin lyase 3 acts on the under sulfated domains of the heparin chain and does not cleave the linkages within heparin's antithrombin III binding site. Thus, a novel low molecular weight heparin (LMWH) was afforded on heparin lyase 3 digestion of heparin due to this unique substrate specificity, which has anticoagulant activity comparable to that of currently available LMWH.