Involved in the biosynthesis of tetrahydrobiopterin, an essential cofactor of aromatic amino acid hydroxylases. Catalyzes the transformation of 7,8-dihydroneopterin triphosphate into 6-pyruvoyl tetrahydropterin. . This is the function of ENSG00000150787 (PTS, 6-pyruvoyltetrahydropterin synthase).