Endopeptidase or
endoproteinase are
proteolytic peptidases that break
peptide bonds of nonterminal
amino acids (i.e. within the molecule), in contrast to
exopeptidases, which break peptide bonds from end-pieces of terminal amino acids. For this reason, endopeptidases cannot break down peptides into monomers, while exopeptidases can break down proteins into monomers. A particular case of endopeptidase is the
oligopeptidase, whose substrates are oligopeptides instead of proteins.