Development of enzyme linked immunosorbent assay for Tripeptidyl-peptidase II and comparison with commercial kits

Sammanfattning

Tripeptidyl peptidse II (TPPII) is an enzyme forming a complex of 4,5 MDa. It is located in the cytosol and participates in protein turnover where it degrades oligopeptides to smaller peptides and tripeptides. Moreover, some of its products might take part in antigen presentation through MHC-class 1. High expression of the enzyme is believed to correlate with tumor progression. A decreased concentration seems to contribute to increased susceptibility to infection. The aim of this project was to develop an enzyme linked immusorbent assay (ELISA) specific for TPPII and compare it to two commercial kits. TPPII was detected through western blot and activity assay to ensure which samples were containing the enzyme. Samples with purified enzyme from different species, erythrocyte lysate and plasma were used to develop an indirect ELISA as well as compare all the assays and evaluate which one performed the best. The commercial kits were based on sandwich and competitive techniques. It was observed that the developed ELISA was able to detect the purified enzyme of different concentrations whereas the commercial kits could not. On the other hand, the commercial kits were able to generate their own standard curve which leads to suspicion that these might be non-specific to TPPII. Though, all assays did detect the enzyme in erythrocyte lysate. This study presents that it is possible to develop an ELISA specific for TPPII using an indirect technique which also performed better than commercial kits.