Human natural killer (NK) cells and activated lymphocytes express and store a distinct subset of neutral serine proteases together with proteoglycans and other immune effector molecules in large cytoplasmic granules. These serine proteases are collectively termed granzymes and include 4 distinct gene products: granzyme A, granzyme B, granzyme H, and Met-ase, also known as granzyme M.

By fluorescence in situ hybridization, Pilat et al. (1994) mapped the GZMM gene to chromosome 19p13.3. Interphase studies with 2 differentially labeled probes for GZMM and the azurocidin (AZU1), proteinase-3 (PRTN3), and elastase-2 (ELA2) gene cluster indicated that the GZMM gene is 200 to 500 kb from that gene cluster.