Phenylalanine N-monooxygenase (, phenylalanine N-hydroxylase, CYP79A2) is an enzyme with systematic name L-phenylalanine,NADPH:oxygen oxidoreductase (N-hydroxylating). It catalyses the following sequence of chemical reactions:
The enzyme uses molecular oxygen and reduced nicotinamide adenine dinucleotide phosphate (NADPH) to convert L-phenylalanine first to its N-hydroxy derivative and then to N,N-dihydroxy-L-phenylalanine. This compound is unstable and loses carbon dioxide and water to give the (E) isomer of phenylacetaldoxime.
Phenylalanine N-monooxygenase is a cytochrome P450 protein containing heme. It is part of the pathway in plants which converts phenylalanine to the glucosinolate, glucotropaeolin, which contributes to the characteristic flavor of brassicas.