| However, rare cases of PKU that result from impaired metabolism of biopterin, an essential cofactor in the phenylalanine hydroxylase reaction, may not consistently respond to therapy. |
| Hexavalent chromium can inhibit benzpyrene hydroxylase activity. |
| Induction of increased benzpyrene hydroxylase activity by flavones and related compounds. |
| In the synthesis of collagen, ascorbic acid is required as a cofactor for prolyl hydroxylase and lysyl hydroxylase. |
| Phenylalanine is normally converted in the human body to tyrosine, another amino acid, by a specific organic catalyst, or enzyme, called phenylalanine hydroxylase. |
| Prolyl 4-hydroxylase and lysyl hydroxylase are known also to catalyze an uncoupled decarboxylation of 2-oxoglutarate in the absence of the peptide substrate. |
