L- Methioninase (methionine γ-lyase) has important biotechnological application because of exhibiting hydrolytic property to catalyze α-γ-elimination of L-methionine to α- ketobutyrate, methaneethiol and ammonia. The abnormality behavior of methionine based metabolic process result ageing, obesity, parkinsons, cardiovascular and cancer diseases among human being. The catalytic activity of L-methioninase could be used as enzyme supplementation therapy for these diseases. This enzyme is resent in wide range of organisms including, plant, bacteria, and fungi. Methioninase secreted from some bacterial species have high therapeutic value because of association with high immunogenicity and low substrate specificity. These enzymes are also used for cancer treatment by depleting supply of methionine from exogenous source to cancer cells. This review is an attempt to briefly describe the sources, mechanism of action, biochemical characterization and its therapeutic applications for treatment of ageing, obesity, parkinson’s, cardiovascular disease and cancer.