Methods and Molecules for Yield Improvement Involving Metabolic Engineering

A cell that expresses a metabolic product, said cell comprising a protein, said protein comprising a first moiety with enzymatic activity and a second moiety capable of promoting degradation of said protein, wherein said first and second moieties are not found together in a naturally occurring polypeptide, said cell further comprising a regulatory system, whereby the level of said protein is reduced upon addition or withdrawal of a factor from growth medium of said cell, wherein said reduction results in enhanced production of a metabolic product from said cell.