Abstract
Abscisic acid (ABA) 8'-hydroxylase (CYP707A) is a cytochrome P450 monooxygenase catalyzing the hydroxylation at C-8' of ABA to form phaseic acid via conversion to 8'-hydroxy-ABA. In previous research, we suggested that 2Z,4E-pentadienoic acid can bind to ABA 8'-hydroxylase if it has a branched C7 hydrocarbon, which is accommodated by the hydrophobic binding pocket, at the C-5 position. However, amino acid residues of CYP707A3 interacting with functional groups of a ligand including the carboxyl at C-1 are unknown. Therefore, we analyzed the functional consequences of the CYP707A3 mutations (K109A, F119A, N207A, K220A, F274A, L343A and K366A) to clarify the interaction between these residues and functional groups of ABA. The CYP707A3 mutants K220A and L343A functioned as ABA 8'-hydroxylase, whereas K109A and N207A showed the largest decrease in activity. The result suggests that Lys109 and Asn207 in CYP707A3 interact with the C1-carboxyl of ABA.
