Modeling the Compartmentalization of Tetrahydrobiopterin Production in the Yeast

Phenylketonuria (PKU) is a genetic disease that leads to an accumulation of the amino acid phenylalanine in the blood, resulting in stunted growth, seizures, and cognitive impairment. Some moderate forms of PKU respond to tetrahydrobiopterin (BH4) supplementation, which lowers the levels of phenylalanine in the blood, and are known as BH4-responsive PKU. Today, chemically synthesized BH4 (Kuvan®) is used to treat BH4-responsive PKU and is the only source of therapeutic BH4 in the US; however, costs can reach $137,000/year for an average patient. Our goal is to engineer the biological manufacturing of BH4 from glucose using Saccharomyces cerevisiae as the microbial host. By taking advantage of the different physicochemical  properties of organelles, such as size, enzymatic activity, and pH, compartmentalization can lead to increased chemical yields. We propose to first localize the BH4 pathway to the mitochondria to investigate the effect of compartmentalization on enzyme activity and subsequent BH4 production levels. We have constructed a mathematical model in MATLAB loosely based off the Standard Compartment Model (SCM) to determine the placement of enzymes necessary for the optimal production of BH4.