The Enzyme Database

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Accepted name: valine N-monooxygenase
Reaction: L-valine + 2 O2 + 2 NADPH + 2 H+ = (E)-2-methylpropanal oxime + 2 NADP+ + CO2 + 3 H2O (overall reaction)
(1a) L-valine + O2 + NADPH + H+ = N-hydroxy-L-valine + NADP+ + H2O
(1b) N-hydroxy-L-valine + O2 + NADPH + H+ = N,N-dihydroxy-L-valine + NADP+ + H2O
(1c) N,N-dihydroxy-L-valine = (E)-2-methylpropanal oxime + CO2 + H2O (spontaneous)
Other name(s): CYP79D1; CYP79D2
Systematic name: L-valine,NADPH:oxygen oxidoreductase (N-hydroxylating)
Comments: A heme-thiolate protein (P-450). This enzyme catalyses two successive N-hydroxylations of L-valine, the first committed steps in the biosynthesis of the cyanogenic glucoside linamarin in Manihot esculenta (cassava). The product of the two hydroxylations, N,N-dihydroxy-L-valine, is extremely labile and dehydrates spontaneously. The dehydrated product is then subject to a decarboxylation that produces the oxime. It is still not known whether the decarboxylation is spontaneous or catalysed by the enzyme. The product, (E)-2-methylpropanal oxime, undergoes a spontaneous isomerization to the (Z) form. The enzyme can also accept L-isoleucine as substrate, with a lower activity. It is different from EC (isoleucine N-monooxygenase), which prefers L-isoleucine.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
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]
[EC created 2010]

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