Tyrosine N-monooxygenase (, tyrosine N-hydroxylase, CYP79A1) is an enzyme with systematic name L-tyrosine,NADPH:oxygen oxidoreductase (N-hydroxylating). This enzyme catalyses a sequence of chemical reactions starting from the amino acid L-tyrosine.
The first is an oxidation using molecular oxygen as oxidant and gives N-hydroxytyrosine:
The enzyme is a cytochrome P450 type of hemoprotein which contains reduced nicotinamide adenine dinucleotide phosphate (NADPH) as a cofactor.
Another similar oxidation step leads to N,N-dihydroxy-L-tyrosine, which loses carbon dioxide and water to give (E)-(4-hydroxyphenyl)acetaldehyde oxime as the final product of the enzyme.
In plants such as sorghum, the product goes on to form the cyanogenic glycoside, dhurrin after the (E) isomer of the oxime is converted to its (Z) form and further transformed.