Bacterial enzymes are antineoplastic perspective agents in oncology. Current strategy of tumor enzyme therapy is primarily based on the strictly defined differences of biochemical properties between normal and tumor cells and more precisely on their different sensitivity to deficit of essential growth factors, including amino acids. The growth inhibitory effects of three bacterial enzymes: glutamine (asparagin)ase, methionine γ-lyase and lysine α-oxidase were demonstrated in in vitro and in vivo using several tumor lines. These results suggest that commercial production of certified standard enzyme preparations and their knowledge-based rational application will provide a new potent anti-tumor preparations employed in oncology.