Abstract: The present disclosure provides recombinant bacterial cells that have been engineered with genetic circuitry which allow the recombinant bacterial cells to sense a patients internal environment and respond by turning an engineered metabolic pathway on or off. When turned on, the recombinant bacterial cells complete all of the steps in a metabolic pathway to achieve a therapeutic effect in a host subject. These recombinant bacterial cells are designed to drive therapeutic effects throughout the body of a host from a point of origin of the microbiome. Specifically, the present disclosure provides recombinant bacterial cells comprising a heterologous gene encoding an improved leucine catabolism enzyme with higher activity and/or specificity for leucine over other branched chain amino acids, such as isoleucine or valine.