Reaction: (+)-abscisate + NADPH + H+ + O2 = 8'-hydroxyabscisate + NADP+ + H2O
For diagram 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 . CO inhibits the reaction, but its effects can be reversed by the presence of blue light . The 8'-hydroxyabscisate formed can be converted into ()-phaseic acid, most probably spontaneously. Other enzymes involved in the abscisic-acid biosynthesis pathway are EC 220.127.116.118 (xanthoxin dehydrogenase), EC 18.104.22.168 (abscisic aldehyde oxidase) and EC 22.214.171.124 (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]