Isoleucine N-monooxygenase (, CYP79D3, CYP79D4) is an enzyme with systematic name L-isoleucine,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-isoleucine first to its N-hydroxy derivative and then to N,N-dihydroxy-L-isoleucine. This compound is unstable and loses carbon dioxide and water to give the (1E,2S) isomer of 2-methylbutanal oxime.
Isoleucine N-monooxygenase is a cytochrome P450 protein containing heme. The product oxime is an intermediate in the biosynthesis of lotaustralin in Lotus japonicus.