ABSTRACT
Proteases play a central role in the degradation of proteins by hydrolyzing peptide bonds. Originally thought to fulfill primarily digestive functions, it is now believed that these enzymes are the principal regulators of many crucial and diverse physiological processes, and that they have a central role in pathological tissue destruction of many organs. Their role in tissue destruction has been investigated in greatest detail in the lungs, especially in relation to the pathogenesis of emphysema. Recent investigations suggest prominent roles for proteases in growth and development and in neonatal lung injury, making a review of the actions of proteases and the factors controlling their expression important when discussing lung diseases in infants. In this chapter we will review the classification of proteases, examine the principal regulatory mechanisms whereby the actions of the enzymes are controlled, and consider their physiological and pathological roles, particularly in relation to pulmonary health and disease. We will end with a discussion of what the future holds in this rapidly advancing field.
