The sequence coding for the catalytic domain of mouse collagenase-3 (MMP-13) was amplified by polymerase chain reaction and expressed in Escherichia coli. The recombinant catalytic domain (CCD), mainly recovered as inclusion bodies, was renatured and purified to homogeneity by preparative SDS-PAGE. The purified CCD degraded gelatin, casein and a synthetic peptide. CCD was not able to cleave the triple-helical domain of type I collagen but conserved the specific property of full-length collagenase-3 to cleave the N-telopeptides. These results show that residues involved in the recognition and cleavage of the aminotelopeptides of type I collagen are located in the catalytic domain of mouse collagenase-3 and that the C-terminal domain is not required for this activity.