GTP cyclohydrolase 1 feedback regulatory protein is an enzyme that in humans is encoded by the GCHFRgene.[5][6][7]
GTP cyclohydrolase I feedback regulatory protein binds to and mediates tetrahydrobiopterin inhibition of GTP cyclohydrolase I. The regulatory protein, GCHFR, consists of a homodimer. It is postulated that GCHFR may play a role in regulating phenylalanine metabolism in the liver and in the production of biogenic amine neurotransmitters and nitric oxide.[7]