Peptidases physiological roles

Enzymes that act on peptide bonds (i.e., peptidases and proteases) hydrolyze peptide bonds in peptides and proteins. We examine first their classification before outlining their localizations and some physiological roles. 

The previous chapter offered a broad overview of peptidases and esterases in terms of their classification, localization, and some physiological roles. Mention was made of the classification of hydrolases based on a characteristic functionality in their catalytic site, namely serine hydrolases, cysteine hydrolases, aspartic hydrolases, and metallopeptidases. What was left for the present chapter, however, is a detailed presentation of their catalytic site and mechanisms. As such, this chapter serves as a logical link between the preceding overview and the following chapters, whose focus is on metabolic reactions. 

The serine hydrolase family is one of the largest and most diverse classes of enzymes. They include proteases, peptidases, lipases, esterases, and amidases and play important roles in numerous physiological and pathological process including inflammation [53], angiogenesis [54], cancer [55], and diabetes [56]. This enzyme family catalyzes the hydrolysis of ester, thioester, and amide bonds in a variety of protein and nonprotein substrates. This hydrolysis chemistry is accomplished by the activation of a conserved serine residue, which then attacks the substrate carbonyl. The resulting covalent adduct is then cleaved by a water molecule, restoring the serine to its active state [57] (Scheme 1). 

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