GZMM (granzyme M) is a serine endopeptidase constitutively expressed in natural killer (NK) cells that plays a crucial role in cytotoxic lymphocyte-mediated apoptosis 1. The enzyme cleaves peptide substrates after methionine, leucine, and norleucine residues, with physiological targets including FADD, EZR, alpha-tubulins, and the apoptosis inhibitor BIRC5/Survivin. GZMM induces caspase-dependent apoptosis through a specific mechanism involving FADD cleavage after Met 196, generating truncated FADD that enhances self-association and facilitates procaspase-8 recruitment for auto-processing, ultimately leading to caspase cascade activation 1. The gene is located on chromosome 19.3, closely linked to other serine protease genes 2. GZMM expression serves as a biomarker in multiple cancers, with high expression associated with improved prognosis in endometrial cancer 3 and thyroid cancer 4. In gastric cancer, GZMM is part of a cytolytic T-lymphocyte signature that correlates with better patient outcomes 5. The protein demonstrates cross-cancer effects and represents a potential therapeutic target, with its expression modulated by healthy lifestyle factors 6. GZMM also shows diagnostic value in inflammatory conditions like ankylosing spondylitis 7.