METABOLIC ENGINEERING IS THE CONSTRUCTION, REDIRECTION, and manipula-tion of cellular metabolism through the alteration of enzyme activities and levels to achieve the biosynthesis or biocatalysis of desired compounds.1 e optimization of production or consumption of a target metabolite oen requires precisely controlled expression of several natural and/or heterologous pathway enzymes such that individual conversion steps in the pathway do not limit the desired product yield (based on dierent Km and kcat values), and that cellular resources and energy are not being ineciently utilized by the cell host. erefore, genetically-encoded tools that enable the control of enzyme expression levels and activities are required for the optimization of pathway uxes.