The ability to inhibit serine proteases is a major focus in the pharmaceutical industry. Serine proteases of medical importance range in phylogenetic diversity from the metallo-proteases, which play a role in pulmonary hypertension, and destruction of the lung parenchyma in emphysema, to those proteases (beta-lactamases), which play a role in the resistance of bacteria to beta-lactam antibiotics. In both the mammalian and microbial systems, the development of serine protease inhibitors has been a focal strategy spurring investigations in the area of serine protease dependent prodrugs that incorporate a bactericidal moiety as well as other classes of metalloprotease inhibitors.