The Enzyme Database

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Accepted name: (+)-abscisic acid 8′-hydroxylase
Reaction: (+)-abscisate + NADPH + H+ + O2 = 8′-hydroxyabscisate + NADP+ + H2O
For diagram of abscisic-acid biosynthesis, click here
Other name(s): (+)-ABA 8′-hydroxylase; ABA 8′-hydroxylase
Systematic name: abscisate,NADPH:oxygen oxidoreductase (8′-hydroxylating)
Comments: A heme-thiolate protein (P-450). Catalyses the first step in the oxidative degradation of abscisic acid and is considered to be the pivotal enzyme in controlling the rate of degradation of this plant hormone [1]. CO inhibits the reaction, but its effects can be reversed by the presence of blue light [1]. The 8′-hydroxyabscisate formed can be converted into (-)-phaseic acid, most probably spontaneously. Other enzymes involved in the abscisic-acid biosynthesis pathway are EC (xanthoxin dehydrogenase), EC (abscisic-aldehyde oxidase) and EC (9-cis-epoxycarotenoid dioxygenase).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 153190-37-5
1.  Cutler, A.J., Squires, T.M., Loewen, M.K. and Balsevich, J.J. Induction of (+)-abscisic acid 8′ hydroxylase by (+)-abscisic acid in cultured maize cells. J. Exp. Bot. 48 (1997) 1787–1795.
2.  Krochko, J.E., Abrams, G.D., Loewen, M.K., Abrams, S.R. and Cutler, A.J. (+)-Abscisic acid 8′-hydroxylase is a cytochrome P450 monooxygenase. Plant Physiol. 118 (1998) 849–860. [PMID: 9808729]
[EC created 2005]

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