Abstract Tripeptidyl-peptidase II (Tppii), is present in most eukaryotic cells. It cuts tripeptides from the N-terminus of peptides and is especially important for degrading peptides longer than 15 amino acids. Tppii also tailors long peptides into suitable substrates for the enzymes which transport and produce the peptides that MHC I present. Increased levels of Tppii have also been found in certain cancer cells, thus it is of interest to determine if Tppii could be used as a tumour marker.The aim of this study was to optimise and evaluate 3 different methods for quantifying Tppii. Western blot, enzyme-linked immunosorbent assay (ELISA) and fluorophore-linked immunosorbent assay (FLISA) protocols were optimised regarding incubation times and antibody dilutions.

Tripeptidyl peptidase II (Tppii) is an exopeptidase which cleaves tripeptides from theN-terminus of peptides. The exact functional role of Tppii is still a matter of investigation. Itis believed that the enzyme is primarily involved in intracellular protein degradation, where itcooperates with the proteasome and other peptidases to degrade proteins into free aminoacids. These amino acids can subsequently be used in the production of new proteins. The aimof this work was to express murine wild type Tppii using E.