MMP-12 lacks a transmembrane domain and furin cleavage site. The zymogen for MMP-12 is about 54 kDa, and is quickly activated to the 45 kDa form, and this breaks down to cascade of active forms, ending with the common 22 kDa form.Stimulated macrophages produce MMP-12, it has also been found in osteosarcoma cells, synovial fibroblasts and lung fibroblasts.
