The present invention provides for a method of producing an oxidation product of an aromatic amino acid in a genetically modified host cell. The method comprises culturing the genetically modified host cell under a suitable condition such that the culturing results in the genetically modified host cell producing oxidation product of an aromatic amino acid. The host cell comprises an enzyme capable of catalyzing the oxidation of aromatic amino acid. In some embodiments, the host cell is capable of biosynthesizing BH4 or MH4 from GTP.
STATEMENT OF GOVERNMENTAL SUPPORT
 The invention described and claimed herein was made utilizing funds supplied by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The government has certain rights in this invention.