20S proteasome trypsin-like activity (T-L activity)

The 20S proteasome trypsin-like activity is one of the three primary proteolytic functions of the proteasome's catalytic core, responsible for cleaving peptide bonds after basic amino acid residues. This activity is primarily mediated by the constitutive subunit beta-2 (PSMB7) and the inducible immunoproteasome subunit beta-2i (PSMB10/MECL-1) (UniProt, 2024). While often considered secondary to the chymotrypsin-like activity in cancer therapy, the trypsin-like activity is essential for maintaining protein homeostasis and is a key component of the immunoproteasome's role in MHC class I antigen presentation (PubMed, 2023). Recent studies have identified a unique 'beta-8-related' (PSMB8/beta-5i) context, where the inhibition of the PSMB8 subunit correlates with non-proteasomal trypsin-like activities that aid in the clearance of protein aggregates, such as alpha-synuclein in Parkinson's disease (PubMed, 2025). Consequently, this activity is a target for both broad-spectrum proteasome inhibitors used in hematological malignancies and selective immunoproteasome modulators being developed for autoimmune and neurodegenerative conditions (NIH, 2024).

Other names

Trypsin-like activityProteasome 20S subunit beta 7 (PSMB7)Proteasome 20S subunit beta 10 (PSMB10)Proteasome 20S subunit beta 8 (PSMB8)MECL-1LMP7beta-2 subunitbeta-2i subunitbeta-8 subunit

Inhibition of the N-terminal threonine active sites within the beta subunits of the 20S proteasome core, preventing the degradation of cellular proteins and the processing of antigenic peptides.