Gelatinase B

This chapter describes the activity, specificity and structural chemistry of Gelatinase B (GelB). GelB is secreted as a proenzyme and has to be activated for enzymological studies. All known modes of matrix metalloprotease activation in vitro result in a proteolysis removal of the N-terminal propeptide involving a cysteine switch mechanism. Gelatin is by far the most favored substrate of GelB in vitro. The abundance of gelatin, and the physiological role of its proteolysis in tissues is not well documented and the substrate specificity of GelB in tissues remains a subject of controversy. The latter has been a major contributor to the fact that multiple names have been given to the enzyme. The GelB protein contains 17 cysteine residues. The propeptide contains one conserved Cys99 that plays an essential role in the maintenance of the proenzyme state by interacting with the zinc ion of the active center and is cleaved off upon enzyme activation. The dimer has a slightly different kinetic of proteolytic activation and 10-fold affinity in gelatin binding.