Apoptotic cell death plays an important role in the maintenance of the normal physiological state and in the pathogenesis of diseases.Granule exocytosis is the main pathway for the immune elimination of virus-infected cells and tumor cells by cytotoxic T lymphocytes and natural killer cells.In recent study,we have investigated the level of granzyme H in patients with breast cancer and in control subjects using enzymatic method.Our study also included the prediction of different sites of granzyme H that play a role in substrate and inhibitor recognition in apoptosis process by using 3D structural model of the enzyme.The research described the possible post-translational modification sites that may help the enzyme in immune elimination of tumor cells.Our study shows that the level of granzyme H was reduced in patients when compared to normal control subjects.There are a number of amino acids that function as substrate recognition sites in granzyme H.However,inhibitors may inhibit their activity and affect the process of autolysis. Apoptotic cell death plays an important role in the maintenance of the normal physiological state and in the pathogenesis of diseases. Granule exocytosis is the main pathway for the immune elimination of virus-infected cells and tumor cells by cytotoxic T lymphocytes and natural killer cells. we have investigated the different levels of granzyme H that play a role in substrate and inhibitor control in apoptosis process by using 3D structural model of the enzyme. The research described the possible post-translational modification sites that may help the enzyme in immune elimination of tumor cells. Our study shows that the level of granzyme H was reduced in patients when compared to normal control subjects. are a number of amino acids that function as substrate recognition sites in granzyme H. However, inhibitors may inhibit their a ctivity and affect the process of autolysis.