Protease that enhances BCL10-induced activation: acts via formation of CBM complexes that channel adaptive and innate immune signaling downstream of CARD domain-containing proteins (CARD9, CARD11 and CARD14) to activate NF-kappa-B and MAP kinase p38 pathways which stimulate expression of genes encoding pro-inflammatory cytokines and chemokines (PubMed:11262391, PubMed:18264101, PubMed:24074955). Mediates BCL10 cleavage: MALT1-dependent BCL10 cleavage plays an important role in T-cell antigen receptor-induced integrin adhesion (PubMed:11262391, PubMed:18264101). Involved in the induction of T helper 17 cells (Th17) differentiation (PubMed:11262391, PubMed:18264101). Cleaves RC3H1 and ZC3H12A in response to T-cell receptor (TCR) stimulation which releases their cooperatively repressed targets to promote Th17 cell differentiation (By similarity). Also mediates cleavage of N4BP1 in T-cells following TCR-mediated activation, leading to N4BP1 inactivation (PubMed:31133753). May also have ubiquitin ligase activity: binds to TRAF6, inducing TRAF6 oligomerization and activation of its ligase activity (PubMed:14695475). Homooligomer; forms oligomers which bind to TRAF6 (PubMed:15125833). Forms a complex with CARD14 and MALT1; resulting in the formation of a CBM (CARD14-BCL10-MALT1) complex (PubMed:27113748). Forms a complex with CARD11 and MALT1; resulting in the formation of a CBM (CARD11-BCL10-MALT1) complex (PubMed:28628108, PubMed:24074955). Forms a complex with CARD9 and MALT1; resulting in the formation of a CBM (CARD9-BCL10-MALT1) complex (By similarity). Shuttles between the nucleus and cytoplasm. Found in perinuclear structures together with BCL10. Highly expressed in peripheral blood mononuclear cells. Detected at lower levels in bone marrow, thymus and lymph node, and at very low levels in colon and lung. The disease is caused by variants affecting the gene represented in this entry. A chromosomal aberration involving MALT1 is recurrent in low-grade mucosa-associated lymphoid tissue (MALT lymphoma). Translocation t(11;18)(q21;q21) with BIRC2. This translocation is found in approximately 50% of cytogenetically abnormal low-grade MALT lymphoma. Belongs to the peptidase C14B family.