exopeptidázy

Exopeptidázy, or exopeptidases, are enzymes that catalyze the hydrolysis of peptide bonds at the termini of polypeptides, releasing single amino acids or dipeptides. They are distinguished from endopeptidázy, which cleave internal peptide bonds within a polypeptide chain. Exopeptidázy can be broadly classified into aminopeptidázy, which remove residues from the N-terminus, and carboxypeptidázy, which remove residues from the C-terminus. Some enzymes act as dipeptidyl peptidases that remove dipeptides from the N-terminus of substrates.

Prominent examples include pancreatic carboxypeptidázy A and B, which function in digestion by trimming amino acids from the C-terminus of dietary peptides. Membrane-associated aminopeptidázy such as aminopeptidáza N (APN, CD13) remove amino acids from the N-terminus. Dipeptidyl peptidáza-4 (DPP-4, CD26) is another well-known exopeptidáza that removes dipeptides from peptide substrates and is a target for diabetes therapies.

Roles and localization vary: in digestion, exopeptidázy work with endopeptidázy to degrade dietary proteins to absorbable amino acids and peptides. They also participate in peptide hormone maturation, protein turnover, and antigen processing by trimming peptides for MHC class I presentation. Subcellularly, exopeptidázy are found in digestive organs such as the pancreas and intestinal brush border, as well as in intracellular compartments like lysosomes and the cytosol.

Enzyme classes among exopeptidázy include metal-dependent metallopeptidases (notably some carboxypeptidázy), serine proteases, and cysteine proteases, reflecting diverse catalytic mechanisms. Because of their role in peptide processing, exopeptidázy are of interest in physiology, immunology, and pharmacology, where inhibitors or modulators have clinical relevance.