Endoplasmic reticulum aminopeptidase 1 (ERAP1)

Aminopeptidase that plays a central role in peptide trimming, a step necessary for the generation of the majority of HLA class I- binding peptides. Peptide trimming is essential to customize longer precursor peptides to match them to the right length necessary for presentation on MHC class I molecules.

Rapidly degrades 13-mer to a 9-mer and then stops. Preferentially hydrolyzes the residue Leu and peptides using a hydrophobic C-terminus, while it has weak activity toward peptides with billed C-terminus.