A fibrinolytic enzyme was purified from the earthworm (Lumbricus rubellus) by column chromatography and identified as lumbrokinase type III. Affinity chromatography and NH2-terminal amino acid sequences indicated that this lumbrokinase III-2 (34.2 kDa) had additional amino acids at the carboxyl terminus of lumbrokinase III-1 (34 kDa). The lumbrokinase III-1 was considerably stable at pH 2 to 11 and at up to 65 degrees C. It had trypsin-like characteristics with high substrate specificity against fibrin, suitable as a fibrinolytic agent. Degradation profiles of fibrinogen by lumbrokinase III-1 and their peptide sequences were also investigated.