The rate limiting step in abscisic acid (ABA) biosynthesis is believed to be the dioxygenase-mediated cleavage of 9-Z-epoxy carotenoids. Isolation of an enzyme that cleaves 9'-Z-neoxanthin to xanthoxal (XAN) from the Citrus cell-free system for ABA biosynthesis is described. The enzyme was precipitated using 45% ammonium sulphate and resolved from lipoxygenase (LOX) by low pressure liquid chromatography on a column of phenyl sepharose. Activity of the enzyme was enhanced from 5.32 to 15.96μg XAN mg-1 protein confirming that 9'-Z-neoxanthin is readily converted to XAN in the Citrus cell-free system.
ASJC Scopus subject areas
- Plant Science