The lysozyme of the marine bivalve, Tapes japonica (13.8 kDa), belongs to the invertebrate lysozyme family and displays both chitinase and isopeptidase activities. We determined the complete cDNA sequence and constructed effective expression systems for this enzyme using Escherichia coli (BL21) and Pichia pastoris. The native and recombinant proteins indicated lysozyme activity and isopeptidase activity, including the proteolysis of D-dimer, a plasminolytic product of stabilized polymeric fibrin. These results will be utilized for the structural and functional study of invertebrate lysozymes, and for the development of applications for thrombosis therapies. (C) 2004 Elsevier Inc. All rights reserved.