The prolyl oligopeptidase family [1,2,3] consist of a number of evolutionary
related peptidases whose catalytic activity seems to be provided by a charge
relay system similar to that of the trypsin family of serine proteases, but
which evolved by independent convergent evolution. The known members of this
family are listed below.
Prolyl endopeptidase (EC 184.108.40.206) (PE) (also called post-proline cleaving
enzyme). PE is an enzyme that cleaves peptide bonds on the C-terminal side
of prolyl residues. The sequence of PE has been obtained from a mammalian
species (pig) and from bacteria (Flavobacterium meningosepticum and
Aeromonas hydrophila); there is a high degree of sequence conservation
between these sequences.
Escherichia coli protease II (EC 220.127.116.11) (oligopeptidase B) (gene prtB)
which cleaves peptide bonds on the C-terminal side of lysyl and argininyl
Dipeptidyl peptidase IV (EC 18.104.22.168) (DPP IV). DPP IV is an enzyme that
removes N-terminal dipeptides sequentially from polypeptides having
unsubstituted N-termini provided that the penultimate residue is proline.
Yeast vacuolar dipeptidyl aminopeptidase A (DPAP A) (gene: STE13) which is
responsible for the proteolytic maturation of the α-factor precursor.
Yeast vacuolar dipeptidyl aminopeptidase B (DPAP B) (gene: DAP2).
Acylamino-acid-releasing enzyme (EC 22.214.171.124) (acyl-peptide hydrolase).
This enzyme catalyzes the hydrolysis of the amino-terminal peptide bond of
an N-acetylated protein to generate a N-acetylated amino acid and a protein
with a free amino-terminus.
A conserved serine residue has experimentally been shown (in E.coli protease
II as well as in pig and bacterial PE) to be necessary for the catalytic
mechanism. This serine, which is part of the catalytic triad (Ser, His, Asp),
is generally located about 150 residues away from the C-terminal extremity of
these enzymes (which are all proteins that contains about 700 to 800 amino
These proteins belong to families S9A/S9B/S9C in the classification of
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