Requires a molybdenum cofactor for activity. NADP+ cannot replace NAD+ and short-chain alcohols such as ethanol, isopropanol, butanol and cyclohexanol cannot replace xanthoxin as substrate [3]. Involved in the abscisic-acid biosynthesis pathway in plants, along with EC 1.2.3.14 (abscisic aldehyde oxidase), EC 1.13.11.51 (9-cis-epoxycarotenoid dioxygenase) and EC 1.14.13.93 [(+)-abscisic acid 8′-hydroxylase]. Abscisic acid is a sesquiterpenoid plant hormone that is involved in the control of a wide range of essential physiological processes, including seed development, germination and responses to stress [3].