Description
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 1.1.1.288 (xanthoxin dehydrogenase), EC 1.2.3.14 (abscisic-aldehyde oxidase) and EC 1.13.11.51 (9-cis-epoxycarotenoid dioxygenase)