HUMAN ADAM-12 (MELTRIN-ALPHA) IS AN ACTIVE METALLOPROTEASE

The ADAMs (a disintegrin and metalloprotease) are a family of multidom ain proteins with structural homology to snake venom metalloproteases. We recently described the cloning and sequencing of human ADAM 12 (me ltrin alpha). In this report we provide evidence that the metalloprote ase domain of ADAM 12 is catalytically active. We used the trapping me chanism of alpha(2)-macroglobulin to assay for protease activity of wi ld-type and mutant ADAM 12 proteins produced in a COS cell transfectio n system. We found that ADAM 12 is synthesized as a zymogen, with the prodomain maintaining the metalloprotease in a latent form, probably b y means of a cysteine switch. The zymogen could be activated chemicall y by alkylation with N-ethylmaleimide. Cleavage of the prodomain at a site for a furin-like endopeptidase resulted in an ADAM 12 protein wit h proteolytic activity. The protease activity was sensitive to inhibit ion by 1,10-phenanthroline and could be eliminated by mutation of the critical glutamate residue at the active site. The demonstration that the ADAM 12 metalloprotease domain is functional may have important im plications for future studies that explore the role of ADAM 12 protein in development and disease.