Involved in skeletal muscle regeneration, specifically at the onset of cell fusion. Also involved in macrophage-derived giant cells (MGC) and osteoclast formation from mononuclear precursors (By similarity). Binds 1 zinc ion per subunit. Interacts with alpha-actinin-2 and with syndecans (By similarity). Interacts with SH3PXD2A. Interacts with FST3. Interacts with RACK1; the interaction is required for PKC-dependent translocation of ADAM12 to the cell membrane. Isoform 1 is expressed in placenta and skeletal, cardiac, and smooth muscle. Isoform 2 seems to be expressed only in placenta or in embryo and fetus. Both forms were expressed in some tumor cells lines. Not detected in brain, lung, liver, kidney or pancreas. The cysteine-rich domain supports cell adhesion through syndecans and triggers signaling events that lead to beta-1 integrin-dependent cell spreading. In carcinomas cells the binding of this domain to syndecans does not allow the integrin-mediated cell spreading. The conserved cysteine present in the cysteine-switch motif binds the catalytic zinc ion, thus inhibiting the enzyme. The dissociation of the cysteine from the zinc ion upon the activation-peptide release activates the enzyme. The precursor is cleaved by a furin endopeptidase.