The secretion of gene products expressed in E. coli is a problem noticeable nowadays. Effect of glycine and L-Isoleucine on catechol 2,3-dioxygenase (CatO2ase) expression and secretion was reported here. Both L-Ile and Gly could increase CatO2ase production. Gly could also cause expressed product excreted into the culture medium. The effect of Gly and L-Ile was related to the composition of culture medium, the concentration of Gly and L-Ile and the culture time. The sensitivity to lysozyme of bacterium cells grown in the Gly containing medium was a little higher and electron micrograph of bacteria grown in the Gly-containing medium showed morphological changes of cell wall and outer membrane. This may have been due to interference with peptidoglycan synthesis by the Gly, and cause passability increase, as reported in other bacterium strains.