20S proteasome trypsin-like and caspase-like subunits (20S proteasome (beta2/beta1))

The 20S proteasome is the catalytic core of the 26S proteasome complex, which serves as the primary machinery for regulated protein degradation in eukaryotic cells [UniProt: P20618, P49721]. It contains three distinct types of proteolytic sites: chymotrypsin-like (beta5), trypsin-like (beta2), and caspase-like (beta1) [PMID: 21664365]. While the chymotrypsin-like site is the primary target for most clinical proteasome inhibitors, the trypsin-like and caspase-like sites are essential for the complete degradation of peptide bonds and contribute significantly to the proteasome's overall capacity [PMID: 26351230]. In malignancies such as multiple myeloma, the high rate of protein synthesis makes cells hypersensitive to the disruption of protein homeostasis [StatPearls: Proteasome Inhibitors]. Drugs like bortezomib and carfilzomib interact with these sites to induce the accumulation of misfolded proteins, triggering endoplasmic reticulum stress and apoptosis [DrugBank: DB00188, DB08889]. Targeting the trypsin-like and caspase-like sites is an important strategy for overcoming resistance to beta5-selective inhibitors and enhancing therapeutic efficacy [PMID: 21664365]. Clinical use of these inhibitors is highly effective in hematologic cancers but is associated with toxicities such as peripheral neuropathy and cytopenias [StatPearls: Proteasome Inhibitors].

Other names

PSMB2 (trypsin-like)PSMB1 (caspase-like)Proteasome subunit beta type-2Proteasome subunit beta type-1Multicatalytic endopeptidase complex

Inhibition of the catalytic threonine residues in the beta1 (caspase-like) and beta2 (trypsin-like) subunits of the 20S proteasome core, preventing the degradation of polyubiquitinated proteins and inducing cellular stress [PMID: 21664365, DrugBank: DB00188].