Involved in auxin biosynthesis via the indole-3-pyruvic acid (IPA) pathway. Also able to convert in vitro phenyl pyruvate (PPA) to phenyl acetic acid (PAA). Required for the formation of floral organs and vascular tissues. Belongs to the set of redundant YUCCA genes probably responsible for auxin biosynthesis in shoots. H(+) + indole-3-pyruvate + NADPH + O2 = (indol-3-yl)acetate + CO2 + H2O + NADP(+) kcat is 0.31 sec(-1) for NADPH with phenyl pyruvate as substrate. Plant hormone metabolism; auxin biosynthesis. A number of isoforms are produced. According to EST sequences. Highly expressed in roots but modestly expressed in the cauline leaves and flowers. Expressed in anthers. Down-regulated by heat stress. Negatively regulated by SPL. No visible phenotype, due to the redundancy with the other members of the YUCCA family. Belongs to the FMO family.