ABSTRACT
Peptidases can generally be divided into two groups: endopeptidases and exopeptidases. Endopeptidases usually cleave an internal peptide bond whereas exopeptidases remove one or two amino acids at a time from the N- or C-terminus of a peptide. The increase in the use of molecular biological techniques has resulted in the cloning and sequencing of many different peptidases. Although general rules can be established regarding the specificity of peptidases and their preferred cleavage sites, the actual pattern of hydrolysis must be determined experimentally with each potential peptide substrate. This chapter focuses on three enzymes that are highly expressed in the lung—angiotensin-converting enzyme, neutral endopeptidase and carboxypeptidase M. Although the specificity of peptidases and their potential peptide substrates can be determined in vitro, the ability of a particular enzyme to carry out this function in vivo will depend on its tissue and subcellular localization.
