Glutathione S-Transferase (GST) enzyme is abundant in mammals, insects, sh and microorganisms, as well as in various tissues of these species, particularly in tissues exposed to xenobiotics from the environment. As a result, the enzyme execute detoxifying function by scavenging a diverse range of xenobiotics, such as chemotherapeutic medicines, environmental carcinogens, and endogenous compounds. In this study, GST enzyme was puri ed from mallow (Malva slyvestris L.) seed for the rst time and the kinetic parameters were determined. The optimum ionic intensity was found in 400 mM Tris-Buffer, optimum pH: 7.0, and optimum substrate concentration was determined as 0.2 mM. One of the biggest reasons for deterioration of ecological balance in nature is heavy metal accumulation in soil, air and water which becomes a major threat to the vital activities of living things. In this study, the inhibitory effects of Fe + 3 , Cd + 2 , Ag + and Zn + 2 heavy metals, which are common in nature, on the Glutathione S-Transferase enzyme puri ed from mallow seeds were investigated. Each heavy metal showed low micromolar inhibitory effects on enzyme activity. I 50 values of the metals were calculated as 0.369, 60.93, 74.602 and 178.22 µM, respectively.