Reaction: L-valine + 2 O2 + 2 [reduced NADPH—hemoprotein reductase] = (E)-2-methylpropanal oxime + 2 [oxidized NADPH—hemoprotein reductase] + CO2 + 3 H2O (overall reaction)
(1a) L-valine + O2 + [reduced NADPH—hemoprotein reductase] = N-hydroxy-L-valine + [oxidized NADPH—hemoprotein reductase] + H2O
(1b) N-hydroxy-L-valine + O2 + [reduced NADPH—hemoprotein reductase] = N,N-dihydroxy-L-valine + [oxidized NADPH—hemoprotein reductase] + H2O
(1c) N,N-dihydroxy-L-valine = (E)-2-methylpropanal oxime + CO2 + H2O
Other name(s): CYP79D1; CYP79D2
Systematic name: L-valine,[reduced NADPH—hemoprotein reductase]:oxygen oxidoreductase (N-hydroxylating)
Comments: A cytochrome P-450 (heme-thiolate) protein. This enzyme catalyses two successive N-hydroxylations of L-valine, the committed step in the biosynthesis of the cyanogenic glucoside linamarin in Manihot esculenta (cassava). The product of the two hydroxylations, N,N-dihydroxy-L-valine, is labile and undergoes dehydration and decarboxylation that produce the (E) isomer of the oxime. It is still not known whether the decarboxylation is spontaneous or catalysed by the enzyme. The enzyme can also accept L-isoleucine as substrate, with a lower activity. It is different from EC 1.14.14.39, isoleucine N-monooxygenase, which prefers L-isoleucine.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
References:
1. Andersen, M.D., Busk, P.K., Svendsen, I. and Møller, B.L. Cytochromes P-450 from cassava (Manihot esculenta Crantz) catalyzing the first steps in the biosynthesis of the cyanogenic glucosides linamarin and lotaustralin. Cloning, functional expression in Pichia pastoris, and substrate specificity of the isolated recombinant enzymes. J. Biol. Chem. 275 (2000) 1966-1975. [PMID: 10636899]
2. Forslund, K., Morant, M., Jørgensen, B., Olsen, C.E., Asamizu, E., Sato, S., Tabata, S. and Bak, S. Biosynthesis of the nitrile glucosides rhodiocyanoside A and D and the cyanogenic glucosides lotaustralin and linamarin in Lotus japonicus. Plant Physiol. 135 (2004) 71-84. [PMID: 15122013]