Abstract: A method for increasing the production of desired hemoproteins is described in which the rate-limiting step in a heme biosynthetic pathway is deregulated to increase the quantity of the rate-limiting enzyme. In yeast, transforming cells with the HEM2 gene increases the quantity of the rate-limiting enzyme ALA dehydratase. Free heme concentrations are reduced in cells by providing heme binding agents that complexes with overproduced heme, thereby reducing or eliminating heme feedback inhibition in the cell. The present invention permits investigation of other factors effecting the heme biosynthetic pathway by reducing interference from heme feedback inhibition within that pathway.